Ruger mini-14 or Saiga .223. Other than the fact that the Saiga .223 is built in Russia, it fits your needs.
2. It'll cost around $400 in unconverted form
3. The AK platform is super simple and easy to maintain,
4. AK platform is the ultimate in reliability
5. I would guess that Izhmash would stand behind it, but AKs are so simple you can fix almost anything yourself.
6. .223 ammo is available is many different weights and bullet types
7. Russian gun, but they build the AK right.
As far as number 1, the AKs butt stock can be left off with no effect on the function of the gun, and so shortens it by around 10 inches or so. The addition of a pistol grip to a Saiga is easily done with home tools in about 15 or 20 minutes, (it requires just grinding or cutting off 3 rivets and drilling out 1 spot weld), and a new Hogue pistol grip (my fave) runs around $20 (the nut is $5). This, and moving the trigger group ($30) would allow the gun to be kept without the butt and still fired, but is very maneuverable. The receiver already has all the holes for everything in the right place.
This one has a folding stock on it ($40), and a different grip than I mentioned, but will illustrate the idea: