You'll probably get a wide variety of opinions on what power is sufficient. It's really a personal thing. Some will say 10x works good for them out to 1000 yards, others prefer something in the 3-15x, and quite a few like the 5.5-22x route. Personally I prefer 12-42x as the eyes aren't what they used to be but mirage can be a factor. I think generally most would agree on 1/4 moa is preferred over 1/2moa. As far as maximum distance it's hard to say as I'm not familiar with your rifles accuracy, your skills etc. If it were me I wouldn't be pushing it much past 500 yards but, as I said my eyes aren't what they used to be. Hopefully others will join in here and lend their comments as well.