I tried the medium 7mm again today. I think the tightness didn't bother my head as much and I'm able to get around, but I'm still restricted breathing. I get a slight anxiety even cause I have the sensation of having to fight to breath. Not good. I'd rather have a large that's a little loose until I gain my weight back than worry about drowning lol.
You seem to be trying very hard to talk yourself into keeping the very bad fitting suit. The suit based on your description is probably 1 or 2 sizes too small on you. Get a better fitting suit that doesn't restrict your breathing at all. It should be "snug" but "comfortable" without pain or breathing difficulties. You should try different sizes and different models/brands. Get what fits and is comfortable. Don't feel bad or guilty about returning the very bad fitting suit.