Hi Dino,
I'm pretty new to this, as well, but I've done a lot of reading.
1. I've read that near the end of summer is best (but not necessary) because, at that time, there is a full "latewood" growth ring and the bark is (somewhat) easily peeled off. The outside layer of wood makes a great bow-back (typically). I did this last August and found that the outside of the tree was extremely porous and the wood was not very good. I shaved down several inches into the tree and found good wood. From what I've read, this is an exception, and typically cutting it near the end of the summer and peeling bark back is a great way of ensuring a good bow back. But I think everyone will tell you that you can cut at anytime of the year... there just might be a little more work de-barking and shaving down to a solid growth ring for the back.
2. Don't know, but I know that there a LOT of bows made with trees less than 10" in diameter.
3. Split immediately into staves and keep the wood covered and off the ground.
4. I'm not sure. I used some old paint that had, more or less, congealed too much to use in the house. I think you're just looking for anything to seal well enough to prevent rapid moisture loss in these areas.