1) You don't need 3 vessels. I use my BK for my HLT currently. It can save save time and hassle however to have a dedicate pot.
2) You could do this, but then you won't have water for sparging. You don't dough in with your full volume.
3) This forum and this section is all the reading material one needs.
Have your brewed extract before or just jumping in all at once. Nothing wrong with that at all. Just gauging experience for what you may or may not currently know.
Tap Room Hobo
I should have stuck to four fingers in Vegas. :o - marubozo's mom