Springmom, maybe you should try an outdoor range.
(Sorry, I couldn't help it. You've mentioned it several times, but everyone still keeps suggesting it.)
My wife and I both have asthma. I hadn't had a problem, or really even remembered having it, since I was 17, and then last year (the week before our wedding, of course) I was cleaning the basement of our new house and suddenly couldn't breathe. I ended up on Advair (I think it was Advair, purple disc thing?) for months until my lungs were right again. Now it has been several months, and I haven't had to use anything.
My wife, on the other hand, has to be on cortical steroids or she uses her inhaler constantly.
Anyway, we both go to an outdoor range, and neither of us has had issues with shooting. I think a big part of my wife not having issues is that the range we go to is on top of a mountain, and the wind is constantly blowing. I think that helps keep the particulates from the ammo away from our lungs.
Maybe you could try getting a big fan and bringing it with you, if your range has electricity. (I know, a fan outdoors sounds ludicrous, but I have friends in Alabama who swear by their "yard fans"...) I've not had issues at my range, but if I go to an indoor range, you bet I'm going to wear a mask. That may help you as well, although it may be hot in the summer.