Neil, do you have any ideas as how I can begin to address this problem? Also any thoughts on establishing a good PSR, making it more habitual.
You raise your shoulder to apply more power. I used to do it too.

All I had to do to break the habit was just set up a cb and stroke it relaxed. See how it feels. Then start adding speed while doing it, staying relaxed. You will be amazed how hard you can hit the cb staying relaxed. Let the cue do the work. You will find that when you do that, your long shot accuracy will increase also!
As to the PSR, it is essentially approaching the table the same way every time. Only adds about a sec or two to your routine. In practice, just "force" yourself for a while to do it. Very soon it becomes natural and you don't even notice it anymore. Make out a checklist of what you want to accomplish for each shot. Such as come into the line of the shot, see what the position routes are off the ball. What position do I want, how best to get there, what speed will I need. Picture it all happening in your mind like it already did happen
All that before you even bend down. At first, it may seem like it takes forever. Again, very quickly, it will be second nature and only take seconds to do. Then, you get down on the shot, take your warmup strokes, verifying everything feels right to you, and then just shoot.
That's just a rough example of what you should be doing. You can refine it as needed.