1. The consensus seems to be 1000lbs. Although, I use straps that are 800-900 but I weigh 200lbs. A 350ish load is actually a 700ish load because of the approximate angle the hammock comes off the tree
. I would only be concerned with breaking strength. Working load is typically 1/3 the breaking strength for saftey, so if you find something with only working load info it's probably safe to assume the break strength is 3x that.
2. 1" straps are going to be more versatile because they will fit more buckles and other hardware made for hammocks and are easier to tie. A 2 in. strap does have the benefit of spreading out the load over a wider area on the tree, but its going to be twice the weight you carry as well, maybe not an issue if you can split the weight over two people.
3. When I first got my hammock I tied a climbing rope to the biner using a slippery half hitch. Then took the "loop" part of the S.H.H. and tied another overhand knot onto the part of rope under tension going to the tree for security. You could probably tie the same knot using webbing as the entire length of your suspension. This worked without fail, and is easy to untie in the morning, but after time you will probably want to move up to another suspension method since it is not that convenient. As far as teeth on the biner go, just be sure to pack your biners outside the stuff sack.
4. If you have seen all the vids you are not missing much. A method gaining steam which I don't think is mentioned in the any of the vids is to have an "all-in-one" system where the whoopie is attatched to the tree strap through a sewn loop or a biner. Also, the tree strap does not have to go around the full circumference of the tree. Alot of people make extenders out of amsteel and other stuff for when their tree straps are not long enough. Some here have stated it is only necessary to have the outside half of the tree wrapped... Just another thing to consider when thinking about strap length.