Yeah, I think at this point you acknowledge that you can't predict with 100% accuracy that you can drink safely - and that is as good a reason as any to quit completely.
It's not a good sign to blackout. Not a good sign at all. You don't want to do that again and the only way to assure that you don't is to not drink again.
I was the same way, sometimes I could have one or two. Sometimes not. I was making really bad decisions and getting into dicey predicaments when I had too many so it was time to quit.