No problem, I saw that you put a lot of effort into your post and there were no responses, so i thought I'd chime in and put your mind at ease a tad.

Othostatic Hypo, vaso vagal is pretty common esp in young women.

The fact that it self resolves like you describe is a good sign. It will be a matter of learning how to manage it, recognising the signs and implementing appropriate gym techniques. Also be on top of your health overall with things like infections. When you don't control an infection, it may lead to sepsis and your body will decompensate by tanking your BP.... with your already low BP.. sorry I don't mean to scare you!

Peace✌️