Which form of a verb do you use when talking about 'everything'?
Tout s'en va for example means everthing goes away but why is it va?
Is it always il/elle form because il can mean it?
It's pretty much the same as with English. Everything goes away, not everything go away. Same with nothing. "rien ne va plus" means "Nothing is fine"
However be careful not to confuse "Tout" and "Tous". "Je les aime tous" Means "I love them all" and it's a whole n'other story with that.