Your fiance seems to have a co-dependent relationship with his mother. At 46, he is unlikely to change it unless he is highly motivated to do so. Another factor is that your future father-in-law colludes with her. He doesn’t tell her to back off. He supports her in her demands to get the house up when she wants it and as fast as she wants it. He didn’t stop her from downgrading his son to his granddaughter. Your fiance seems to be following in his dad’s footsteps and doing whatever makes his mom happy. She has a very powerful position in this family.
The fact that he would postpone your marriage to build his parents a house is probably symbolic of how it will always be. Her demands come before his happiness – and yours. You don’t have an ally in your future father-in-law. Only you can decide if your fiance has enough of the other qualities you are looking for to make the terms of this relationship worth it. Maybe he does. He must be sweet indeed for you to have juggled this situation as long as you have.
I suppose you could sign on for a lifetime of competing with his mother but that usually ends badly. You could also try asking to take the reins of your fiance’s finances to see what happens. It’s just possible that she doesn’t think he can handle it and has been waiting for him to have a partner she could trust to take care of him. It’s not likely but it is possible. Your other choices are: — love him for his other qualities and join with him in keeping his mother comfortable or — leave and look for someone who wants you as his true partner in life.
It’s probably just as well that the wedding was postponed even though it was painful at the time. You have had the time to really consider what kind of life you will have if you do marry this man.
I wish you well.