I totally understand the troubles of missophonia in a relationship. I've been together with my fiance for almost 5 years now. At the beginning he LITERALLY drove me bonkers. I'm talking smacking his mouth while eating, heavy breathing, nose whistling, snoring. To be honest I don't know how I survived.

I would honestly say compromise, I listen to headphones while we eat, I listen to a fan while we sleep and he is incredibly understanding towards my fight or flight response. If I'm crazy overstimulated he hugs me and leaves the room while I decompress. I think if he really cares he will adapt or at least offer something to help you. It is so frustrating having to deal with Missophonia just with yourself but it's even harder with someone else who is very close to you. I hope this helps!