In fairness, if a relationship is about soul mates, and the love between you blossoms and flourishes, then, when you are kids are grown up - at university and in their jobs and relationships, the two of you will remain. Perhaps he likes the bit about being with you, and likes the kids, but wants to set controls over what he is letting himself in for.
If he's ever read Mumsnet, lol, he might be thinking about those kids in their mid- twenties who won't move out and who bring their partners round all the time to stay over. He might think is that what his new home will be. If he's not, as an adult, used to family life, it might seem like a commune.
You'd probably be better continuing in separate homes, as that is the bit he's probably perturbed about. Apologies if you have explained, and I haven't read the whole thread, but what were you thinking married life was going to be...living in his new place? He rents it out and lives with you?
It not too much of a stretch to think he's bought a place of his own to keep something separate that is his, and a safe depository for his money. It seems to me that there is s disconnect in his head. Engagement to you equates to a romantic notion which pleases you and keeps you sweet and committed to him. Blending homes equates to losing his money. He obviously hasn't thought about marriage being a legal contract to share all that you have.
If he does well at work, he might go on to earn five times what you do. He might not feel it's satisfying to put it into saving accounts for your kids and to fund higher education for them, as they mature.
I'd say to stay engaged and see if the love he has for you is enough. Ask yourself what one poster postulated - and be brutally honest with yourself: Are you looking for someone to financially support you and your children?