I'm not sure that NL win rates are measured in terms of BB/hour.... if they are, I don't know what to tell you to shoot for. Compare yourself to JD. If you are doing half of what he is doing per hour, you're probably doing ok
For 1/2, assuming the buy in is $200, I would recommend having a $4000 bankroll to be safe.
Personally, I think $3000 is fine, but if you go by the 5% (20 buy in) rule, than you are looking at $4000.