I have not read this entire thread, so I'm sorry if part this has already been mentioned.
Farting on stage is fine, as long as you don't "gamble and lose" when you do it. Come on.....its happened to everyone at least once.
Whenever possible, you should try to retain your gas if there is a chance that it will be so bad that other band members, and possibly the audience, will actually be able to taste it.
I recall an incident when I was younger. I was playing in a garage band, and we were performing for our friends and neighbors, in a garage, who would have guessed, and the guitar player Tim, started letting them rip. It was so bad that it actually gave me a sick headache. Its been decades and I still remember the odor.
It was Winter, so I was wearing a knit cap at the time. When I put it on again three days later, the fart odor was still all over it. I had to throw it away.