To guide using ST4, you'll need to select "On-Camera-ST4" as the telescope type in the Telescope Settings window. Then connect the ST4 port from the selected guide camera to the ST4 port of the mount -- no USB involved.
With ASIAIR (today), you cannot concurrently control the equatorial mount and use ST-4 for guiding. It would definitely be a useful option (someone else on this forum has also asked for it).
Also, after doing some digging on the forums, I saw another user had the same problem that I'm having. I'm using the synscan hand controller for the telescope driver, he suggested the beta.
I will try that as well and report back.
I also just picked up a few extensions for the 290 mini, and I'm going to try my 72mm doublet as a guide scope for my 127 Ed.
thank you for all your help and I will let you guys know what happens.