I’ve had shoulder problems in the past (never diagnosed - but once I couldn’t bench or shrug anything more than 50% 1RM for over 6 months without pain).
However, what made a big difference in the life of my shoulders was doing something similar to the 100-rep protocol. Three or four times per day (nearly every day) I would do a couple sets of unweighted arm circles.
I started doing a set of 10 with arms straight out from sides and fists moving in a circle about 6" in diameter. Then a set of 10 about 18" in diameter. Then a set of 10 with full range. Then do one set in the opposite direction.
I worked up to doing a total of 60 reps 3 times/day.
It’s important to find a “groove” that is pain-free. Try not to just bull through the pain for the first couple of reps until it loosens up. Find a way to do these so even the first rep has no pain.
You can experiment with arm-speed and hand position throughout the circle to alleviate pain and “clicking”.
After a couple of months of this I was able to resume benching, and have been benching heavy (for me) and pain-free for two or three years now. My bench has gone up from an abysmal 200 to an almost respectable 285 in that time.
PS: I also discovered many rotator cuff exercises when I started reading this web-site about 18 months ago. I think they’ve been important in keeping my shoulders healthy as my numbers increase.
I hope this helps.