I guess there's a good reason why all Olympic shooters use a bow sling. I didn't realize it was that dramatic. I do the same things you probably do to reduce bow hand torque: hold the bow primarily with my thumb and forefinger, with the other fingers just touching the back of the handle. Even then, if I forget and press with my thumb on the side of the handle, it will throw my shot off to the left. I would guess from your experience that there are subtle pressures that are difficult to feel that we exert on the bow handle even if we only grip the handle with the thumb and forefinger.
My own solution to shooting better in general is to try to increase my awareness of what my body, in this case the bow hand, is doing during the shot, which is a lifelong process. I do know, from what little progress I've made so far that it is possible to become aware of sensations you had no awareness of before, if you open yourself up to discovering them.