Although everyone has a different amount of flex in his/her joints so there is no singular right or wrong answer, in general, I would agree that without seeing your hand in person, there is too much reverse. My span is 4 11/16 x 4 9/16 (lefty) and I am a ZERO for thumb pitches...no lateral, no forward, no reverse.
If you have too much reverse, you may be squeezing to hang onto the ball, causing you to bend your thumb and causing pain and potentially tears down the road.
I would visit your local shop that is certified (and different from the shop that currently drills your stuff) to get a 2nd opinion at the very least. I would go in and advise them (PSO) of the situation, but do not let the PSO see your specs. Let the PSO fit you from scratch and see how close the 2nd PSO is to your current PSO.