It's rather funny. I have a PhD and am the main character and yet I have trouble following the story myself. The cancer certainly doesn't help. However, Saw IV and V actually take place simultaneously. When Jeff kills me, Detective Strahm then kills him, resulting in the remainder of V.
No, for several reasons.
The first is simple. She's an emotional wreck. She projects her own insecurities onto others. She believed she could never change, and therefore believed that no one else could. She took my legacy and turned it into elaborate execution devices with no offering of freedom. Even when she did, the offering never actually worked. She was truly a killer.
However, I could forgive all of that if it were not for one thing. At my death bed, she made me question my entire philosophy. She had been through three games, and never seemed to learn her lesson. She failed me so many times, and yet I still don't hate her. If anything, I'm disappointed.