@diomit, I can relate as well. I know exactly the feeling, as sometimes a yawn will satisfy the feeling of need for air, while other times it's like it stops short, no?

I mentioned Buteyko Method of breathing in the OP, but just to provide you a possible aid with your breathing, it might be worth it to try elements of the breathing method through a Buteyko practitioner like Patrick Mckeown or through learnbuteykoonline.net. While not every element of it is for everyone, I think everyone can take some element of the method and apply it your individual situation.

For example, I do the "steps" exercises 3-4 times a week, and have trained myself to breathe just through my nose at all times, even during exercise, which has greatly improved my breathing. I would offer it as a suggestion for you to look into. They have various "rescue" exercises when an air hunger episode is especially bad.

I don't know much particularly about mold issues, but have you attempted any sort of mold detox regimens, whether through diet or other methods? Exposure to mold can certainly affect the lungs to different degrees depending on degree of exposure, but wondering if you've looked into possible detoxes specific to mold.