Even though I'm not that far past amateur myself, I'll see if I can help a bit.
#1: I would imagine that it depends what kind of finish you use, but I've not had a problem with this as long as you let it dry thoroughly. Although, I have had an issue with the Fiebing's black and dark brown dyes getting a kind of greenish sheen when it dries. I don't know why this happens, but if you use Tan-Kote as a base layer, it seems to help.
#2: Rubber cement is what most people use, I just apply it liberally to both sides and then clamp them together between a board and a my work bench.
#3: This also shouldn't be a problem especially if you put Tan-Kote or Neat-Lac as a final finish.
#4: I get my leather from Weaver who are significantly cheaper than Tandy, but you do need a sales tax licence to order from them. They have great customer service, and are fairly quick in shipping orders.
Hope I was of some assistance, even if it is a bit like the blind leading the blind.
Spencer