For what it's worth.....
I have both of the same "problems" you are having on my newly rebuilt (this winter) Limit TA60 and new HD actuator. I can't get below 21psi, that is with the wg rod all the way out to zero tension, then adding 1/2 turn.
Also, I'm still creeping a bit and when I sent it in, Chopper felt it was because I had the stock actuator and the hole was 1" as mentioned above. I notice the creep more on this baseline 21ish setting than when I had it turned up some. Tends to creep 2psi or so. If I set it to 24 it will more or less stay right there.