I can't help but wonder, maybe I'm supposed to leave. My marriage is a disaster, starting with the first day. Adultery, verbal abuse, you pretty much name it, I've lived through it. The only reason I stay is financial. I want to stay home with my kids while they're little, and I can't do that if I divorce him.
I think your insight about losing the remaining reason to stay (financial security) may be spot on (not necessarily sent by God, but that you're recognizing that the deal you made may not be the right one for you or your children).
Staying in the kind of situation you describe is likely to send the message to your children that they should live that way too -- setting off on a different course while they're still young may be preferable. Don't do anything rash or tip him off (even if you're not physically afraid of him, it sounds like he wouldn't be above robbing the bank accounts/creating more debt to make things worse for you). Get copies of all your current financial statements and look for local women's groups that offer free legal advice.