Yes, they'll fit Remington 700, 721, 722, 725, & 40X.
Yes, the medium ring should work fine. If you're using external scope covers such as Butler Creek, I would recommend a high ring, item 750700.
No, Talley only makes these in 0moa.
No, this mount will not fit on the Ruger American rifles. You will need the Ruger American Centerfire mount, found here: https://www.opticsplanet.com/talley-ruger-american-savage-riflescope-mount.html.
Just keep in mind that this search also includes Savage. Mounts that will fit your Ruger American will end in 725.
Due to your objective lens size (50mm), I would recommend using the Talley 750700 1-Piece Hi Base & Ring Set which will allow for enough clearance of your objective lens. You can find the Talley scope rings by using the link below:
https://www.opticsplanet.com/talley-750700-1-piece-hi-base-ring-set-remington-700-30mm-style-black-finish.html
No, the model 710 does not use the same mount as the 700. It does, however, share the same mount as the 770. These are for the 710:
https://www.opticsplanet.com/talley-lightweight-alloy-scope-mounts-for-browning-howa-remington.html?_iv_parent-gun-make=remington&_iv_parent-gun-model=remington-model-710&_iv_gun-make=remington&_iv_gun-model=remington-model-710
Yes they will.
No, unfortunately not.
Higher rings are recommended for 50mm.
High rings for 50mm and larger objective lenses.