Rumpelstiltskin's point of view...because I couldn't resist and it rounded out the story. I doubt the additional theory involving Zoso will play out, but I enjoy it all the same.

***
Zoso's bet

Rumpelstiltskin had never considered himself a betting man. As a man, he had never risked anything, so he never lost, right? The one and only thing he had ever took a chance on, was Milah. His timid proposal had been the most daring thing he had ever attempted. He loved her so, he thought of her everywhere, saw her everywhere, and he wanted nothing more than a simple life with her, everywhere. If he had been a more astute man, he would have seen her, as she was, not as he wanted her to be. A wild spirit, who would never been content to the simple life he so desired, she would never be his. But he took a chance and she had said yes.

This could have been, now that he looks back, because she had said her family had nothing and well, he had a trade. He had a home, simple, but efficient. He loved her, that was clear and was certainly nothing like the rather morose and easily angered father she described. He would care for her.

But she would never love him.

There it was spelled out in ink. Milah will accept, but my daughter will never love him.

Rumpelstiltskin closed the book and opened it one more time, just to make sure he had not imagined it. Nope, still there. He swore.

Rumpelstiltskin, the new Dark One, had been played. He had known that the moment he had stabbed Zozo, with his own dagger. But he hadn't thought just how far back this had been in motion. His daughter...

Rumpelstiltskin, now the Dark One, full of new found power, yet all alone in the world now, Milah, dead by his own hands, her proclamation of non-existent love for him, still ringing in his ears, and his son, Bae, whom he had dropped into an unknown world, which he still had been unsuccessful several years later, in securing a portal to, suddenly was full of daring.
He had nothing more to lose and he had always been a curious man at least. He turned the page.
His eyes scanned the page. He will love his son, but not more than his own life, then his power. No checkmark here. Rumpelstiltskin supposed Zozo had been killed, before he could really be sure that this was true. Yet it had been, and he placed a checkmate next to this statement in sadness.

There were further predictions about various people in the nearby area that Rumpelstiltskin did not recognize or know them well enough, to decide how true they were likely to be. So he scanned down further. The next page was empty save for one, large print, prediction.

Love destroys more lives than it saves.

The next set of pages were divided down the spine. True and not true. Tallies were present on both sides. The True side was full of many more tally marks the the Not True side.

Zoso had been counting. Counting how many lives had been destroyed by an act of love versus how many had been saved. His hands trembled as he counted the total. Almost a 2-1 ratio, favoring love as destruction.

He pulled out a feather pen from Zoso's desk. He dipped it in the ink beside it. One mark, he added for Milah. His love had destroyed her, unwilling to let her go to someone else.
Then he added one for his son, whom his love of self preservation, had left all alone in a world, which Rumpelstiltskin still could not find a way to.

There he wept for hours, truly believing as Zoso had, that it was hopeless. Life was such a burden, if love was so unkind. What was worth living for?

***
It was many, many years before Rumpelstiltskin, began to try again, to find a way to his son.
A little girl, was crying in a great room, full of straw. Some ridiculous lie had been made up about turning straw into gold, she said. Rumpelstiltskin knew that it had been a trap to draw him in. That this unloved, abused little girl, had lied through her teeth to a king, to get Rumpelstiltskin's attention.
"You can do, it though, right?" She inquired. "If you do so for me, then you will save me from death."

"All magic comes with a price."

"I know." Her desperate eyes searched him. Rumplestiltskin felt for a second that he was looking into his own desperate eyes, as he had stabbed the Dark One. A chill went down his spine.

"Usually, it destroys a person. Magic. Just like love." Rumpelstiltskin had offered, trying to get her to see the foolishness of trying to barter with him, for anything. "I have a running tally, you see, of just how many people have suffered from both."

The girl seemed to ponder this. "Perhaps, you are just not making the right kind of deals. I could help you."

Rumpelstiltskin had to admit, he was not the most creative or intelligent of men. Zoso's books that he had found over the years in his castle, which he had taken over, seem to suggest that he had been much more so of both, then Rumplestiltskin would ever be.
The Blue Fairy's words to him the night he lost his son, replayed in his ears. "Such a curse is beyond your abilities."

A horrible thought occurred to him. This girl would kill him, if she knew how that would benefit her. Unloved her whole life, there was nothing to stop her. Then he really would never see his son again. So, he drew his enemy closer.
"How about if I teach you, magic?"

The girl narrowed her eyes. "And what would be the price for that?"

Rumplestiltskin smiled. He reached for her, her touch zinged with untapped magical potential. Here was the brains and the talent for his curse. She would be his curse maker. A way back to his son. One less tally for the left side of the book.

"I would need you to design something for me, once your training had progressed far enough to assist me."

"Design what?" She asked cautiously.

"A curse. One that will help me reach the land where my lost son resides. A curse that will prove Zoso wrong. That love doesn't have to destroy the thing you love the most." Rumpelstiltskin gave a wistful look. He showed her the tally.
She didn't question any of his words, but then she didn't seem to believe them either. She scoffed as though she didn't believe such a thing was possible. Yet, her eyes flickered with a spark of hope. "Throw in some straw transformed into gold tonight, and we have a Deal."

"Nice to be working with you then..." He offered, searching for the name of the girl.

"Cora."

Unfortunately, the king demanded another night of straw into gold. She had nothing left to offer, her services already procured. "Your first born, will belong to me." Rumpelstiltskin offered.
Cora didn't even hesitate. "Deal."

She didn't love the king, why should she care for their first born? But somewhere in there, there was a potion to prevent children and an unhappy king who was stuck without an heir. King George said she was poisoned, but Rumpelstiltskin expected she did it herself. Her father had long ago taught her, screw or be screwed.
The king dismissed her as wife. Cora couldn't have planned better. She was free, and she already had more things leaving, then she came in with.
But, Rumpelstiltskin would not be cheated out of his deal, so easily.
He might have introduced Henry and Cora.
And then magic and unwanted true love destroyed her.

She loved this man and their daughter. She would give up anything, even a heart to protect that. Making deals with dark fairies, and ripping out hearts left and right.

Rumpelstiltskin should have just left her barren.

At least one day, she gave him an incredible curse. Only, it required something to be cast, that neither of them possessed. Something that they loved. And Cora had been heartless for too long.
"Just screw over some already miserable soul, then offer them a way out, and they will practically do it for you." Cora muttered without a moment's hesitation, cold and unfeeling.

On his way out, a girl on horseback rode by, almost knocking him over. At first, he was certain she was afraid of him, but when he looked, she was more afraid of being seen. A young man waited on a hill for her. Secret lovers.

Rumpelstiltskin, his head still covered, merely, chuckled. "No harm done, dearie."

Cora would lose. She had bested him over and over again, cheating and lying, and backstabbing in every way possible these days. But he would win. The beautiful baby, now woman could still belong to him. He knew how to recognize a desperate soul.

And he didn't have to wait long to make his first move.

***
Zoso was wrong. He had made many deals that he did not understand. Zoso's had not been the last. He should have chosen his words more carefully. His, no Cora's, big magical experiment, was more than he could have envisioned, yet she had technically given him everything he wanted. A whole town of people, to study, to watch, to see if love had indeed destroyed them. Unable to leave, like rats in a maze, he could tailor their lives to his liking.
But even he had been a rat too, until Emma came into town. But he knew now, and the results were still to be determined. And Cora, a hopeful little girl no more, was certainly waiting for the chance to make her move on him, for using her daughter and her husband, to enact her curse.

He would never admit it to Regina, but Cora had still won. His son was out there in this land, but he was unable to get to him, and a whole lot of people's lives had been twisted, in attempts to prove Zoso wrong. And Rumpelstiltskin wasn't sure anymore that he was. Cora never thought he was. Love is weakness. As he sat watching young Henry sleep, desperate to see his sleeping grandfather again, even at risk to his own safety, he traced a finger over the checkmark she had made next to that statement in Zoso's book.

Then with a red ballpoint pen, Rumpelstiltskin, added one more huge tally to the left side, to the True side of Zoso's original tally. It was hard to say whether it was for Cora, Regina, Henry, both of them, Snow, David, Emma, or his love and weakness, Belle. Or it could have really been any other of the town's people. But the tally, being red and much bigger than the others, it really didn't matter. It was clear enough to Rumpelstiltskin.

If Emma died or she failed, in her upcoming task, her open end of their deal, if she failed to save this world, well, then it stood for everyone. If she couldn't manage, with all the crap she had been put through, all the name of love, to prove Zoso wrong, then no one could.

And then it would also stand for Rumpelstiltskin.