I've been going through a lot of bone broth, love the stuff, but not before exercise. I will make a point to have some with my breakfast before my 6am group training session. I know many here do fasted exercise but that's never worked well for me, once I've been primal a few more months I will try it again.
I will look into your suggested supplement ideas. The cramping doesn't happen every night - and I don't have varicose veins or twitchy legs, so am pretty confident that I am missing something in my diet - but when it happens it is pretty intense. I do have regular morning poops already