1) Yes you can currently get every skill in the game and make everything if you take the time to train it all up. Which likely will take about 1000 played hours, if it were my guess.
2) Ive seen some non populated areas, depends on how far away you want your neighbors. Because totems dont decay, you will see a lot of areas not active, but with totems.
3) Basketry is the only one you HAVE to have, if you want some of the recipes. Basket recipes are only on creation right now, so make sure you got basket recipes when you make your toon.
4) Yes they raise up while you play, and they lower too. You wont be stuck. They do take a while to change (months to go 10 points).