So it seems like the focus of your rehab has been to release the pec/anterior shoulder and strengthen the mind back. If this hasn’t provided relief after 3-4 times of performing it then my personal opinion would be to change tactics.
So If we think about the anatomy of the lat, it travels from the anterior shoulder to the lumbar spine. If we try and lengthen it at one end (I.e. at the shoulder during OHP) it will try and shorten at the other end (the lumbar spine) to feed you some slack. This will create and overextended lumbar spine during shoulder flexion (OHP). When at rest, this can also cause rounded shoulders and kyphosis as the anterior is being pulled down and forward to again create more slack in the system.
So give yourself a good banded lat stretch like this picture. But notice in the picture his palm is facing down, the stretch is more effective with palm facing up. During the stretch dont let your lumbar spine compensate by extending, you want to maintain neutral to flexion in the lumbar spine.
Accumulate a few minutes on each shoulder then re test a light OHP.
Prior to the stretch do a couple of OHP in the mirror and get a friend to take photos, then compare after the stretch.
We are looking for full external rotation of the shoulder and no lumbar spine extension after you have done the stretch.