The car? Seriously, the car?! Hopefully your tubes are tied because there's still a chance you can get pregnant at your age. I'm not trying to be cute. I mean it. You really should make sure you can't have another kid. Also, if it were up to me you'd have your kids taken away so they don't have to witness a woman being treated so horribly. Because being around you and him ... they are learning that love is getting treated like crap. It means there's little chance they will have normal families when they go off on their own.
How do you care more about what to do about a car when he puts boobs on his phone, likely cheats, uses you financially, and is lazy? Are you that worthless that you are begging to marry this? Don't bother answering any of this. I'm done.