Yes, you have enough compressor...
Responses to your questions:
1. I typically recoat the whole panel when block sanding. I give the body filler an extra coat before putting down two coats over the whole panel.
2. See post #29 in this thread. its a cab seam, but should answer your question.
http://67-72chevytrucks.com/vboard/s...=509519&page=2