Compromise can be a really hard thing. I am curious to know what his changes are to your plans. Sometimes my husband accuses me of saying no to something, or saying I don't like something, just because he was the one that came up with the idea. I'll tell you the truth though, sometimes I think he is right, often I will have something in mind and have a immediate no response to his suggestion. For example, recently I was sewing a felted bag. I showed it to him and was telling him how the design was going to progress. He suggested I make a flap instead of leaving the bag open, and my first reaction was no way. Then I really looked at it and considered the idea. I ended going with his suggestion. lol.
I guess my point is that sometimes a suggestion is helpful. I don't know either of you, so I don't know what is really going on here. If he is railroading your dream then definitely stand up for yourself. I work on really considering my husbands suggestions because I have found it is good sometimes to be open minded and consider all options, as well as making my marriage happier.
My husband and I are together 24/7 because we both work at home, and we have also built a house together (and I do mean literally built), so I really understand where you are coming from. It can be hard to be together so often, and I have read that a stressful thing like building a house together has led to a lot of divorces in the diy community.
Some people may consider my approach stroking a mans ego...I just know what works for me. I mean, does your husband really really care how your sewing room is designed, or does he really just want to feel valued?
Maybe you could get him into a hobby and tell him you will help him develop his own space for it.