Aw, hugs to you. As I was reading through the thread, I was stifling my impulse to tell you about a friend who was in a similar situation. Her DH ended up committing suicide, leaving her with two teen boys and a ton of debt she didn't know about. Then it occurred to me that money aside, mental illness aside, you (and I mean the universal "you", but you, too) should never enter into or continue a relationship where something as big as your desire to be a SAHM is impossible from the start. I felt the same way you do about it: That was my intended "career" once the kids came along. (I did have a paying career until then, but I always knew that whether I was 22 or 42, when the kids came, I wouldn't be going to an office for awhile.) You are young, and you will find someone who can support your dream to raise your kids the way you want to.
(But yeah, it does sound like he's looking for a woman to marry who will take care of him the way his mom has. You can still love him, and be his friend, and help him out sometimes, but if you think you won't be happy married to him (not for lack of love, but b/c of the day-to-day situation of having to work, not enough money, not being with your kids, and having to drive him everywhere, nevermind the concern about secret spending and who knows what else), don't do it.)