I've tried streaming a couple of times, but I find it's not my cup of tea. I get such a stage fright from it, and canøt concentrate on drawing, so I feel it worsen my quality. I would rather make speed paints and such, then I can also post them after the page is published, and the wohole spoiler issue is avoided!
But to answer your questions:
1: A little spoiling is actually good, because it creates interest. But if you are worried, a spoiler warning is probably the best way to go around it. And if you are in doubt if something is spoiler or not, you don't have to worry if you have already said it. And then people can't come and complain, since they have been warned
2: I can't see why? If you don't want to talk you can just play some music in the background or nothing at all. If there is only one or two in the chat, engagement is propably needed from your side, but the few streams I have done or attented, I didn't think it got any more personal than normal chit chat or talking about nerdy things if you find you are in the same fandom as a viewer or something like that.
3: If that's what you need to keep draw go for it! If it is stupid, but it works for you, it ain't stupid! Also, your feelings are never fake. It's how you chose to deal with them that matters