1. I'm not sure if there is a difference between buying them seperately or in a bunch. All you get now is the gauge/adapter, and the cartridge removal tool.
Theoretically, all you really need is the adapter. You can buy a gauge from a plumbing and or air conditioning parts store for about 10 bucks. You can use either really sharp needle nose pliers, or two hex wrenches.
3. It's used for taking out the inner piston on the scm. unless you have a reason to change out the scm1 to the scm3, you won't need it. I bought one, because I changed out about 4 or 5 of them for the local aka users.
I'd strongly urge you to consider looking at DC (destructive customs)(www.destructivecustoms.com
) for a testing and parts kit. AKA charges what I consider very high shipping and handling charges, while Jared is much more reasonable. He may not have them listed on the web page, so send him a PM - Destructive Customs - to see if he has them.