If you look at the Ruger Scout, that rail appears to be uniform height above the bore and appears to me to clear line of sight across the top of the receiver, so you'd want the same rings front and back. I just don't have one to know for sure. I do have that same scope on my Steyr JC Scout, and it's about 1.366" (34.7 mm) diameter front and back. You would think identical low rings front and back would be fine, therefore. They just need their center heights to exceed 0.683" above the rail.
But rather than guess, I suggest you call Ruger to get the straight poop. Their chart doesn't provide center height.
Re powder: Bullet velocity depends on the average pressure at its base during its whole trip down the bore. There are two extreme opposite ways to get the same average pressure: high peak pressure with a low muzzle pressure, or low peak pressure with higher muzzle pressure. These are what fast and slow powders tend to get you, respectively. Because peak pressure imposes a safety limit, you just can't safely get to as high a velocity with fast powders as with slow ones, so they can't drive a bullet as fast as a slow powder can. But that slow powder will give you more recoil than the fast powder when it is held down the same velocity. For a recoil calculation, if you don't have QuickLOAD, with its convenient recoil calculator, this free PDF file from SAAMI
has the necessary formulae.
What you discover is, yes, faster powders are more efficient. That is, a higher percentage of the chemical potential energy is tanslated into the bullet's kinetic energy. The figure of merit is called the Ballistic Efficiency (BE), and it is expressed as a percent. That improved efficiency is why, for a given velocity, you have lower charge weights of the fastest powders that can safely do it than of slower powders needed to get to that same velocity.
For .30-30 performance levels, you may find .30-30 performance powder is best. IMR 3031 would be a good choice. By dint of felicity or kismet, take Hornady bullet number 3031 and marry it to IMR 3031 powder. In an 18" barrel, QuickLOAD thinks you can load it to 2700 fps with a very slightly compressed load, but follow the manuals.