I don't know what state you're in, but here in CA, my daughter was eligible for Medi-Cal, because her parents were divorced, even though my husband (her stepfather) made good money, but wasn't eligible for health insurance (temp to hire situation). His income wasn't counted.
I appreciate your desire to have a healthy and peaceful marriage, but I still think your best bet is to relocate until/unless Dad gets the kid some help. As a mental health nurse, you already know you can't help people who do not want to be helped. And if you rock the kid's boat too hard, he may use that very big knife and kill you while you sleep.
