I can answer the Ventress question. She was supposed to feature heavily in the 7th Season, and earn redemption. But it was a short season so they had to drop it.
Instead the turned the story into a book: Dark Disciple.
The long and short of that story is that the Jedi Council decide to assassinate Count Dooku. They send Master Quinlan Vos to infiltrate and then surrender to Dooku so he could pledge himself to Dooku, fall to the Darkside and become his apprentice. And then turn on him. Ventress and her team of bounty hunters are hired to attempt to infiltrate Vos. Along the way Ventress and Vos fall in love, and the bounty hunters get their asses kicked by Dooku, who uses Force levitation and Lightning, as a spinning Sith whirly-gig to fry Boba Fett and others (the animated story boards are on YouTube).
Vos and Ventress eventually duel Dooku and they lose quickly. Ventress escapes and Dooku tortures Vos for days, and then takes Vos as his apprentice and for the next months trains him in the Darkside. Vos falls to darkness and becomes very powerful; powerful enough to threaten Dooku on near even terms. There are escapades with the Jedi who do not know Vos is deep under cover. Vos defeats Kenobi but lets him go.
The ruse is later sprung and during the three-way duel between Vos/Ventress vs Dooku, their ship crashes and Dooku is badly hurt. Vos and Ventress manage to then defeat Dooku and are about to turn him over to the Jedi when Dooku gets loose, and sends an ultra powerful Force Lightning attack at Vos, Ventress pushes Vos out of the way and is struck by the Lighting and nearly instantly killed. Dooku escapes and Vos is left mourning Ventress' death.
A sad end to a great character whose life was defined by tragedy. But in the end she came back to the light and was loved.