I'm not a doctor either but I have a few thoughts.
1. Cancer is not the main thing that gets smokers, though it gets a lot of us/them. The main thing is COPD and emphysema. Unlike cancer, this is SLOW damage, so any day you do something to improve your lungs is a day you are fighting to prevent COPD.
2. Exercise, besides helping your lungs, releases dopamine or endorphins or something, I don't remember which. I know I get nervous about exercising every since I've had 2-3 shortness-of-breath attacks from exercising on warm days when I was out of shape and had smoked 1 PAD for a number of years. But I know that my fear of exercising is doing me 1000 times more harm than good, so now that I'm
vaping and my breathing is getting better (my night wheezing went away and I could climb ONE flight of stairs without getting horribly winded) I'm trying to work on two flights of stairs. With HOURS in between. (It helps that I work on the third floor of a building, so I take the stairs 2-3 times a day with hours in between.)
So I'm building up my lungs without scaring myself. Next will come long walks around my not-flat-ground block.
3. Tobacco has some very powerful anti-anxiety agents in it that are not nicotine. If your anxiety is worse when
vaping, you might want to also try Swedish snus or WTAs. Look for the WTA sticky on ECF. Also, since snus is not inhaled, maybe you should consider using it with vaping to cut down on vaping but still get your tobacco fix.
4. Vaping has possibly been shown to have a slight constricting effect on the lungs for about 1/2 hour, IF you inhale, so you might want to vape up ahead of time and avoid vaping right before singing. [Edit: this is still nowhere near as bad as smoke inhalation.] Also, the good parts of vapor are absorbed through the mucous membranes of the mouth and nose, more like nicotine gum, so you could cut down on your inhaling and pretend you're puffing on a pipe or cigar and still get the benefits of vaping.
5. Recently I read an interesting article that we should spend a few minutes a day visualizing ourselves as we'd like to become, so I've been trying to visualize myself more physically fit and calmer. This does not calm me down, but it does motivate me to exercise just a teeny bit more. It moves my "comfort zone" slightly towards health. Not a lot, but I'll take whatever I can get. And when I exercise, I'm calmer -- I feel more like I "own" myself.