That's a good question.
For current :
http://web1.whs.osd.mil/mmid/military/miltop.htm Rank/Grade link (iirc)
As for the number of "Ex's", ....who knows? It doesn't matter, really. If the "Anti-Rummy's" can't make enough racket out of the pool of ex-Generals; then there's, like, a jillion ex-colonels and Majors out there to cherry-pick from. They will have plenty of ammunition.
LOL ... the Good News is: "All the ammunition in the world will not make a bit of difference." Rummy has to please one man. That's just the way it works. :)
I liked Rummy's more current attack
"I don't have time to read all your books..."
Thank you for the very interesting stats link. You are right of course about the unending downstream of brass that can be "cherry picked" to suit RAT purposes. We can only hope that the GOP will have their own ammunition for counter attack.