"It sounds like his big dream isn't to be married to you its to own his own home, which he will probably kick you out of if you ever split up because he will see it as his."
I agree with this. My x definitely wanted a grand home to reflect his lofty status in life
He was happy to plunder me like a resource for years. I gave him my savings (at the beginning). I paid for groceries, DIY materials, I sanded and painted rooms in his house, I bought plates, cups, placemats, rugs, utensils, you name it, it's all still there too!! not to mention bespoke curtains for a bay window, some furniture, parking permits outside his house for his parents and siblings) council tax, things for the kids. He not only left me with no rights, but he left me with no savings, no opportunity to work outside the house, no time (all of my labour went in to raising the children and cleaning his house) so basically when I met him I had a good job and a deposit for a flat and I had a future and I had opportunities and by the time he'd finished with me I had two dependants, no career, no income, no savings and no opportunities and o time. And he saw this and right and proper. My reward for all of this was in his view the temporary roof over my head, always dependant on his whim and his mercy, and there was no discussion because he genuinely seemed to believe that I ought to be grateful to him.
That's what you have now. You are the me I was ten years ago. PLEASE tell his financial abuser that you wouldn't marry him because he's not worthy of you. It's a dollar short and a day too late. He might marry you but he's not a nice man. So it'd be a financial relief but you'd be married to a very unpleasant man. You have a job!! Your children are growing older not younger. You have options and you have opportunities, providing you don't continue to sink your time, your energy and your money in to feathering his nest.
Sorry I've written such an essay but it is awful to see nice women (and I can tell you are) make the same mistake I made.
Also, the whole thing about niceness, whenever I attempted to get my x to relinquish some of his rights, and to be fairer to me, he would question my niceness. Such a master manipulator stroke. ie, a 'nice' woman would meet all of his needs without question. ANy woman who attempts to meet some of her own needs is somehow a cold ruthless selfish cold hearted gold digger!?!?!?!?!?