Congrats on your SR556.
If you have a new gun, then you should have the re-engineered bolt carrier group. You'll be able to tell it by the rear end of the bolt carrier. The edges have been radiused to eliminate hard contact with the leading edge of the buffer tube when the BCG cycles.
There will be a little shiny showing on the leading edge of the buffer tube at the bottom where the pin is. A little wear showing there is normal. Excessive wear is not.
All piston guns (by nature of their design) experience a little bit of carrier tilt. I think Ruger has really done it right with the SR556.
If you are still worried about tilt, then there are a couple of after-market buffer tubes available that claim to eliminate carrier tilt entirely. I understand that PWS (Primary Weapons Systems) has a really good buffer tube. Theirs run from about $100 up to about $150. I've been considering one for my own SR556, but my stock tube shows so little wear that I can't really justify the expense.