You have a strong desire to find out what your problem is, and I totally support you in that endeavour, however, I would not recommend you go for invasive testing at the moment. You've had a series of tests most of which, it seems, don't worry your doctors. Mitral valve prolapse can be troublesome and you should have an echocardiogram every 6 months or so to keep an eye on it.
I have many of your symptoms and was rushed to ER last Sat morning at 5am. I was experiencing the weirdest bursts of adrenaline, giving a feeling much like being on a roller coaster at max. fear/excitement... but no roller coaster. Before that I'd been sleeping soundly without a care. In ER the episodes came and went in waves, causing me bouts of shuddering and intense emotion. They did several series of tests, and all came back negative. They solved my problem by sedating me.
I also have a stressful job, and have known for some time that it irritates my condition, but I now realize to what extent. I almost certainly have a panic disorder, though you might not guess it from the way I perform in my job. I'm right there in the thick of it, always pulling round situations from certain disaster. The problem comes when I have the opportunity to relax. Then I start to unravel physically, with PACs, PVCs, stomach discomfort, chest tightness etc.
Our situations/histories are different in many ways, but we're both suffering from stress and we've both been tested for what we believed was the problem.
I plan to see a psychologist this week to see what I can learn there. If it's an issue of managing different stresses (that cause physical symptoms), I'd rather go for that than doing invasive tests which, in themselves, could cause heart problems.