The answer to the half slayer blood thing is, seeing how the powers that be took her powers away she was helpless so they gave her half of the strength of the Slayer. The lesson in all this is that love is found in the most unlikely places and in the most unlikely situations. As for Angel's knowledge, the memories are coming back to him slowly because the PTB are making it that way. As for the rest, it will unfold in time.
Willow awoke on a large fluffy bed and studied her surroundings. The room was dark and gothic with a few red candles back around the bed. Willow racked her memory of the previous night and remembered the bite. She instinctively thought to feel her neck but chains coiled tightly around her wrists.
"Of course you wouldn't make it that easy for your victims would you?" she asked spike who was lounging in the corner.
"Well, if I did that I would have to fight you."
"I thought you liked getting caught and when it was with fists and fangs." She retorted smartly.
"Well, that's true," He strode towards her. "But I just want to play a game."
"If you'd just say you want to torture me it would go easier."
"Okay," He said picking a knife up off the bedside table. "if, you're going to be difficult." He slid the knife along the first layer of her dress. "Then so can I." He paused and rubbed the blade against her collar bone. The blood beckoned to him and he leaned his head town to taste it. The blood tasted like innocence and pain with a rich unknown flavor.
"get off of me." She spat really wishing she had her powers. He smiled against her chest and kept his mouth there as long as he could. After a minute, he pulled up.
"You know your discomfort is really satisfying." He smirked as she tried to dislodge him.
"As satisfying as it may be Spike, she is my toy. You have that witch to play with."
"Fine, spoil my fun."
"That's what I was made for." Spike walked out grabbing the knife and looked at Willow before exiting.
Angelus waited until Spike had shut the door and climbed on top of Willow. "Now, what should I do with you? I hear you are a witch so I guess I could use the tortures they used on them, but then again I'm a creative person so I'll use something different. So tell me," He cut the second layer of the dress. "How do you feel about fire?" He inquired bringing a candle near her face. Worry filled her features as she tried to fight Angelus off. "I thought so." He smirked and then poured the hot wax where the cut was that Spike had made. She didn't scream but she did let tears escape her eyes. Angelus leaned down and licked the tears up her tears off the cheek. "tears taste almost as good as blood; they're like an elixir." She tried to dislodge him but he squeezed his legs against hers. Something went through her and she moaned. "Enjoying this are you?" He asked smirking.
"I-I shouldn't. these-these are naughty thoughts and I can't do this." Before she could go into one of her babble-fests, Angelus crushed his lips against her and kissed her roughly, exploring every last bit of her mouth, tasting her essence. He pulled up and hurried out of the room.
As soon as he was out of her sight he leaned against the wall.
"I don't understand. She's just like all the other's I've tortured." He muttered to himself. "She reminds me like Drusilla and I can sense darkness."
"You know, they say that talking to yourself is a sign of madness." Spike smirked leaning next to him on the wall. "And you are right about the tree, she has darkness in her. Dru said that after she lost her little girlfriend, she soaked up all the magick from the books and tried to raise a Satanic temple."
"Impressive." Angelus commented. "If she's got all the power maybe I should be harder on her."
"Let me go a round with her." Spike said gazing longingly at the door.
"fine, you hurt her then…that's just fine. Just make sure she lives."