Any .308 Winchester ammunition.
100-550 or so
The best you can afford.
Contact Ruger
You will have to contact Ruger
Remington 700 308?
"Best" is a subjective term that will be based on your pocketbook and what you are using the rifle for.
The best you can afford. Leupold is always a good choice.
.310. Call Ruger to verify.
100 meters.
100-450
100-1000 or more depending on specifics