Well first I thick Kyle will not kill Cassidy but he'll in somehow get into Cassidy's memory and find the way he killed Sara and save it into a holographic memory and that he'll black mail Cassidy like he did and threats him if he don't let the family alone he will expose him and put him I jail.
About what Jessi found in Nate's computer I think she knew the fact that Kyle and Cassidy are brothers and probably Nate too that's why he was interested in Kyle issue.
Then Nate wakes and hurts Jessi he'll shock her or try to kill her or something like that and in some way Amanda manages to run away so she goes back to tell Kyle. Mean while Kyle goes to the rack to save the family and by mark's help he figures out away to do it.
But there's one missing IT'S JESSI so Amanda tells him that she is in Nate's apart and probably he killed her and that Nate is in a rage and ask him to stay and don't go that she's gone and that she wants him back since everything is over now, but he tells her that after what they passed through together he can't leave her that he cares about her that he loves and can't live without her.
So Kyle goes to Latnock no one was there just like in the first episode of season 3 everything is gone he listens to Jessi's heart beats here is it but it's getting slower he starts a deception to find out where is she she's locked in Cassidy's office, she's wounded she is dying here heart is stopping Kyle restarts all his power revive her but it doesn't work he's losing her he lost his hope and as usual it come someone to save the day it's Foss he asks him to kiss her, but Kyle says there's no why she's already dead but Foss insists so Kyle does it at that moment a masse circuit of energy lightens the city of Seattle. And here she is, she opens her eyes she's alive but after this whole power loss Kyle and her are so tired and frustrated they just passe up and wake up on the hospital where all the family and friends were waiting for them. So Foss took them to the hospital. Then life goes back to normal at the Tragers Kyle and Jessi decides to take along tripe out of Seattle. They continued their training together with Foss.
And finally it all ends up three or four years later it's josh and Andy's wedding everybody was there Kyle and Jessie are back for the wedding they got married and they have tow cute children a boy and a girl "Adam & Sarah", Declan and the girl from Latnock are married to she became a Prof at the university and Declan is now ruling his father's company since he can't get back to basketball. Lori now is pop star she kept writing songs and her CDs are hitting the world but she out of work now, she's pregnant, her husband mark now is working with Steven they established a company working in computers hardware. And of course you all asking about Amanda she's teaching piano and ruling her own conservatory and yes she's got married to a guy who is musician too he plays violent and she has a very sweet young man seven months old his name is.....definitely "KYLE". Oh how do I forget Nicole the tender mother she is working at a height school as a social consular. Hey wait I said it's josh and Andy's wedding but where are they they're too late everybody is waiting for them, oh not they're in josh's room, what are they doing, WHAT??? They're playing G-force!!!!!!!!!!!! What is this they never grow up even though they are 21 years old unbelievable.