@oneservant That's a lot of words for a pretty simple issue... you already know it's fucked and wrong or you wouldn't have come here and put this much effort into typing all of that out.
I think you know this dude is trouble. Is this the kind of guy, with these type of ideas about money and his mother, that you want to commit to for the rest of your life? To possibly raise children with? How do you explain that dad lives in a van and there's no money for field trips because grandma doesn't wanna pay rent and hasn't had a job in a decade?
People will show you their true colors. Its up to you to believe them.
edit
Based on your post history it seems you dove into this very serious relationship very quickly. General rule of thumb is that it takes a year or two before you
really get to know someone. If I were you... I'd take this as a lesson in the future. Don't rush into these things for this very reason, and cut your losses with this dude now before it becomes a much bigger issue for you down the line.