If your partner were my son and I saw him being treated like this by you and heard him being spoken about like this by you, I'd be very, very strongly advising him to leave the relationship. And I'm far from being an interfering mother.
I'd be very concerned too, about why he was staying in a relationship with a woman who sounds almost contemptuous of him. What had gone wrong that he put up with being treated like that?
You really do come across as thinking you are better than him. You may say that you don't but how you write about him shows you do. "He can't paint, bless him". How patronising. "She can't cook, bless her" - how does that sound. Patronising and sexist.
You're rushing into this. You and your 4 children need time alone, not the upheaval of a new partner a wedding and a new child in such a short amount of time.
You don't really mention the children or the relationship between your partner and the children.
If he was my son I would be worried that you see him mostly as potential financial security, despite the thousands you have put into the home. BTW if you have really put thousands into the home without protecting it, you have been very foolish indeed.
I know how hard it is to recover from an abusive relationship. The fear and anxiety, wondering how the hell you ever got into that position, the fucked up thinking during and afterwards. You need time and space to recover. You don't need to hurtle into a new relationship and this time scale is hurtling.
Do you feel safer regarding your abusive ex because you have a man in your life? Is that partly what is driving this. You've been through such a frightening, terrifying experience that having a man-as-protector brings you some security even if his chewing drives you mad. I could be way off the mark, but I've seen it happen before.
I really don't think you should go ahead with this marriage, you need to look after yourself and much more importantly, your children, who you hardly mention. I don't think you'll listen to me or anyone else here sadly.