This could go one of two ways. chelseamorning fully explained way #1, which is a definite possibility that’s what’s going on here. but, i have a friend who was in a similar situtation (her boyfriends family was vile, horrible to him all his life, and cancerous to their relationship), so i think it all depends on the vibe you get from him.
is he just really, really down on himself? does he outburst (about the ex, etc) and then feel horrible about it and apologize? is he genuinely interested in wanting a new life, but is just not confident enough that he can do it: hence, not really committing to trying. if he tries, he could fail and, in his mind, he most likely will. if this is the feeling you get from the situation, i say all is not lost.
or is he seemingly confident in other areas of life and just whiney with your relationship? does he blame you/tell you to do things with no remorse? does he seem to only be talking about changing just to make you feel better with no original intent to follow through? if so, go re-read what chelseamorning said, as she’s probably on the right track.
my advice on the other scenario (that he has horrible self-esteem issues, but really wants to change himself) is to postpone all wedding plans. Tell him directly that you love him, you want to always be with him, you think he can be an amazing man – he has what it takes. And to be that amazing person, he has to stand up for himself. Get a new job, tell his family flat out that they are not part of his life, and cut away from them (severing all ties is best for him, these sound like poisonous people). Tell him you’ll help him turn his life around and you believe he can do it.
If you don’t think you can have this conversation, or you think he’ll be furious to hear it, I’m not sure how far your future will go with him. you’ve got to tell him honestly that this is a dealbreaker (because it is!) and you’ll know the next step from his reaction to that. as hard as it may be, you’ve go to listen to your gut here, not your heart. i really hope this works out well for both of you, with the minimal amount of pain (although, since you said you’ve grown from all previous relationships, i KNOW you’ll be great in the end)