1. ThreeBond? Some kind of sealant for the differential plugs? Some people use Loctite or some other comparable thread locker (i.e. Permatex Threadlock, can be found at Kragen). I've seen other people use teflon tape. I didn't use anything at all and i'm not leaking fluid from my rear differential. The most important thing is to torque the plugs correctly (most important to me anyways). 36.2 ft/lbs for both the fill and drain plug.
2. Overboost.com - Power Maintenance - Brake Bleeding
Check there, some good tips and pictures (not subaru specific, but most calipers and brake systems work the same way).
3. You'd have to get a different color brake fluid. When the brake fluid being bled changes colors, you'll know it's all purged.
(now the problem is finding a different color...)
4. ? No idea, but i'm sure someone chime in eventually.