Alright, to answer the questions...
You don't cut below the bore cut (which does go all the way through the tree for whoever asked) when cutting the straps, if the wedge is in and tight it will keep the tree from leaning back onto the bar because there is solid wood above and below the wedge at all times, there's nowhere for the tree to lean back on, no kerf. I understand what you're saying Grubs, but if the tree is small enough to tear your strap wood, you should just be doing a one cut slice to drop the tree, not messing with a quarter cut. I suppose you could cut below the bore, but then you're back cut would be lower than your face cut and you'd barberchair pretty bad. These cuts never leave a good looking stump, but you can always flush cut it later if you're really that anal.
Your face cut goes slightly above your bore cut, at least thats how I do it, I want all the hinge wood I can get with a lot of these tree's. If its pretty straight, and the weight isn't off center, then you can use the bore cut for you're face cut level. But remember, your straps should be cut higher than your face cut.
As far as how close you come to your bore cut with the strap cuts; you'll need to overlap your strap cuts slightly with your bore cut to make sure you don't have fibers left still holding the tree, if you don't overlap you end up with 2 sets of fibers that can make the tree unpredictable, -_- if the two outside dashes are your strap cuts, and the inside dash is the bore cut, you still have wood holding the tree from falling at the "l" (-l_l-). So you need to overlap the strap cuts, just not too much.
Here's a picture of how it should look, the black lines are your bore cut, and then strap cuts, the red line is where your face cut should be, just on the other side of the tree. Also with this tree, its probably big enough to wedge over with the standard method, but its the best pic I could find. Cut the strap on the right last, it'll be safer the way the tree is leaning.
I don't have anything to be able to take video, otherwise I'd post one...