Smoke can be very acidic, I used to smoke cigars occasionally but would have to spit out my saliva routinely, if I swallowed it my stomach would be on fire the next day. you should definitely get checked for asthma if you haven't already, but know that it can just make gerd worse.
I experienced what I thought was shortness of breath too when my GERD first started, but I think it was actually I just didnt understand what was happening in my esophagus - not saying that it is the same for you though, shortness of breath is not something to just brush off lightly.
An xray is a start but you need more tests tbh. GERD is definitely a top contender, maybe a hiatus hernia, I suggest seeing a Gastro-enterologist and possibly an Enterologist as well.
Heart disturbances happen with GERD too, I get them all the time, scared me a lot at first but now Im used to them. Again though you should get some tests, I had an echo and EKG which were normal so then I could relax that nothing serious was going on, I imagine its harder to brush it off if drs haven't looked into it at all.
I've gone through my fair share of light headedness and easy fatigue too, although I still don't really know why it happens. One thing I've found helps is doing relaxation techniques when Im feeling faint or tired, it allows my body to recuperate a bit and I feel a lot better afterwards.
GERD, Anxiety, Depression, Rolling Hiatus Hernia, Esophageal Hypersensitivity