My thought what was the point in the 1st place. If it shoots good just rat tail file or chains saw file . I would remove the front sight and belt sand the notches off. That would save filing down a new front sight. What does the rear sight look like
This is what I have found for myself. It is just more comfortable to use crossed sticks than to try to use sandbags. You have more adjustment. I also have had success with a bench with a threaded for adjustment rest built in. Give different options a try until you get what works for you.
TC Hawkens were / are notorious for a ball skipping the rifling occasionally. The shallow Button cut rifling is more effective for maxi ball type ammo. The groups you are getting very good I would not worry