.65/.58 is roughly the Nash equilibrium of a game that is close to, but not exactly heads-up with 300/600 blinds and even stacks of 5000.
This is the actual game: you pick two numbers, one the percentage of hands you push with, the other the percentage you call with, based on column C
here. When you are on the small blind, you must either go all-in or fold. If the small blind pushes to you on the big blind, you of course either call or fold. Your two numbers cannot change, even if the stacks become uneven.
As far as I can tell, this simplified game comes very close to real poker. Given the ability to min-raise, or the option to change your numbers once the stacks become uneven, has little effect. Eastbay might be able to elaborate a bit more if you're interested.
Yes, a reasonable all-in or fold strategy will essentially nullify any advantage a great player may have over you, especially with high blinds. Look up Sklansky's "the system".