I'll pass this on to any guess having throttle issues with FSUIPC. I played around doing different things until this finally worked. After assigning throttles, go to the calibration page. At each block for each throttle, there's a button that says reset. It will clear the min mid and max axis data. Just by doing this and leaving it alone, I get full throttle range. Works like a charm now, give it a shot.
I can't get it to scroll down or display fully even with scaling off to get to options in the manager