1. I stream to vimm regularly and dlive rarely and twitch once upon a time ago, 3speak I don't use.
2. I'm considering using a restream service to add twitch back in, as the people are there
3. I would pay a very small amount. (less then a VPS at Digital Ocean or Linode)
4. Chat combining I would need to do one way or another
5. Probably, certainly as a "benefactor"

Hope this info helps.