Is my Vacuum too low?

I don't get near that amount of vacuum on mine. Mine runs a bit over 11. I think you are worrying about it too much. I'm no expert, but here's how I set mine, and I then took to a shop to have it tuned on the chassis dyno. A/F mixture was good at idle when I got there, so apparently I did ok dialing it in myself.

I started about 1.5 turns out like you did. I then adjusted mine out while watching the vacuum gauge. When I hit max vacuum, meaning it was no longer climbing, or as soon as it dropped even a little, I stopped adjusting. If vacuum doesn't climb as you are backing them out, then dial them in a bit and watch for the needle to drop on the vacuum gauge and stop there. In my experience, you want them set right at where the vacuum peaks out and no longer climbs. I had my timing light running so I could closely watch RPMs for changes while adjusting too.

Granted mine was on a 750 cfm Speed Demon with 4 corner adjusters, but the concept is the same.