He's pretending to be the dedicated, long-suffering husband and if he takes the money that's been offered to him, he'll be proven to be a lying, greedy SOB once and for all. A lot of people still believe in him. They won't if he takes that money. If he sticks it out and makes sure that Terri dies, he'll get her insurance money and he can maintain the farce that he did it because it was what she wanted.
Michael Schiavo is quoted as asking “When is that bitch gonna die?”; by Terri's nurse, Carla Iyer in a deposition in September of 2003.
Unleash the hounds.