It is very telling that MS turned down that offer. Even to allow Michael to inherit Terri's estate when she dies the Schindler's offered him just about everything a person could imagine might be a motivator for his continued quest to have Terri killed. I would love to know if he has a life insurance policy. I'm not a gambler but dog gone it, there's some reason why he's so determined for her to die.
He wants her DEAD and has for so long now, and he will inherit her estate anway when she dies. Therefore, offering her Terri's "money" was a nonstarter.
It's called revenge for their not letting him kill her back in 1993. Think about it. The man is a sicko.