Generally, you don't want to regulate idle RPM by adjusting the idle mixture hex link. You mentioned that you ran out of adjustment to get it lean enough to idle down.
You really want to adjust RPM with the butterflies and then correct the idle AFR with the hex link.
"Short" on the hex link is lean and I believe that's because your idle check valve is set so high. 9 PSI is too much in my opinion for a naturally aspirated setup. 1-2 PSI on that should have your adjustment in a more friendly place.
I've found with that check valve at 1-2 PSI, you can leak the barrel valve at 7% of the engine size and be almost right on the money every time. Just a flat or two one way or the other and things are running well. So, engine size X .07 and there's your percentage (or very close).
Spud