Geez this is scaring me. A couple years ago I began experiencing ALL the symptoms you just listed there and it actually started after I took an Ephedrine pill to stay awake (Something I never did before). I too ended up in the hospital that night and thought it would be my last based on how I was feeling. I know my uncle had a heart condition that he needed surgery for and the Mitral valve prolapse sounds familiar.
I can relate to when you're laying on your back and start falling asleep and then suddenly feel as though you can't breathe. I had actually started experiencing heart pain a year or 2 before the incident that pushed it over the edge.
I actually reported these same symptoms and more but they just thought I was delirious as the heart test came back ok so they tried to put me on anti-depressants instead in their messed up desire to give me some form of diagnosis.
What test did they do to detect the MVP? I had an EKG which came back fine.