Since dry hopping primarily adds aroma, do you need to adjust the amount of hops you add to the secondary if your alpha acid levels differ from the original recipe?
Only? I kind of doubt that, I'm sure there's plenty of crossover. You'll get some flavor and aroma from the 60 min addition, and you'll get some bittering from the later additions (except maybe dry hopping, and possibly hopback/flamout additions).
You can say, though, that 60 min additions are primarily for bittering, and the rest are primarily for taste and aroma. Absolutes don't hold true.