AkDan, Without seeing it is really hard to help. It sounds like you have way too much tension in your string hand and wrist. This is something the "deep hook" can help with. Not sure what you mean by a "gorilla grip". The real definition of a deep hook is that your index and middle finger has the string in or very near the first joint (from the tip) of the fingers and that those finger tips are pointing back at your throat at full draw.
IF you are shooting with a deep hook AND a relaxed finger release, there should be NO pain and no callus build up. I did a video a while back called "release tips" that may help give you some ideas. You can find it on Youtube by doing a search for TheMoebow1.
Bottom line suggestion would be to work on keeping your string forearm, wrist and hand as relaxed as possible all the way to full draw. Then when ready to shoot, you will find that just starting to think "relax" the fingers and the string will be gone. The fingers get flipped out of the way (with NO pain). But if you are getting to full draw and thinking "open the fingers to shoot" you will get a good "rub" of the string going across the fingers. No one can open their fingers fast enough to get out of the way of the string and that causes the problem. The problem just gets worse as the string gets closer to the finger tips too.
Arne