Ataloss don't know if you are still reading this. There seems to be a lot for you and your partner to sort out. Why is he holding back some of his income? Will your MIL pay her share of the expenses when you all live together, what will she do all day, will you still be near her friends? - will MIL help with childcare etc so that you don't have to do everything? Will you have your own sitting room when you move or share with MIL?
Meanwhile, in your current situation. If you are paying equal shares into the bank, why are you not also doing equal shares of the work? Does your partner do the gardening and DIY as his share? It sounds as though he might be amenable to doing more and maybe you need to talk about having a rota or something, so that you don't get tired and can enjoy each other's company. If MIL is not going to help with housework, you could consider getting paid help for cleaning and ironing, or you could reduce your hours and do it yourself, deducting an appropriate cost from what you pay into the joint account. Starting again in later life is never easy, but neither is being on your own. Do you get out together for a meal, or a drink, go to a show etc? - learn to talk - Make a list of what you love about him - think of tennis - it is easier to fight for every point to win the game, than to give up and have to play another whole set!