His behavior was as an ex-husband your right. I would personally have handled it differently from the beginning. First of course not hitting her (if he truly did that). Second I would not have gotten involved with anyone and certainly not have children with someone else. However, once I felt like I could not handle the situation anymore and wanted out, I would have given her the divorce (although not a fan of it). Most importantly I would have given her to her parents (especially once they begged me not that it would have gotten to that point). His situation and behavior is so far from how I would of handled it.
It was also far outside any honest interests. Allowing Terri's parents to try to feed Terri orally would have disipated much of the resistance Michael faced. Further, it would offer the possibility that Terri might asphyxiate and die from the effort, resulting in Michael being rid of her sooner. So why such resistance?
Unless he was trying to kill her not because she was PVS, but because she wasn't.