#1 Score Books ---> http://www.bullseyegear.com/bullseye...&cat=22&page=1
#2 LE or Police is a catagory you put on your SR-1 (entry card), unless you have a lot of shooters and catagories it dosnt really matter.
#3 Yes you can use your revolver in the CF matches
#4 Again, yes you can use (45 cal) revolvers in the 45 Cal Match.
The exception is the EIC match (earing points toward you Dist. Pistol) where you have to use a 1911 or Ber. 92. (Rules govern these pistols keeping them like the service pistols).
Here is something else that will help you, I have the USAMU Pistol Marksmanship Guide (Bullseye Pistol Shooting) on .pdf file, if interested PM me with your e-mail address and I'll send it to you.
One thing about Bullseye (and just about any other compitition, you're gonna find great people who will be more then willing to help you get started in the right direction, don't be afraid to ask.