John,
You are fine driving around with the tune you have on your supercharger with no belt producing boost. You won't be under boost. So your car is fine. Is just like an NA car. Even if your car did run a little lean under throttle, it's not the same as it would be under boost. When you get an ATI harmonic balancer, your best bet is to get one that has not been used on another car. You want to make sure yours is snug and tight on the snout of that crank. If you are going to use the Sean roe kit, that would be better than pinning it. Sean's kit is as close as they come to having it keyed.