You and I are close in age: I turned 76 in August!
Not sure what "reverse shoulder surgery" but I gather your doctor has assessed that it will be a beneficial solution for you. I'll definitely pray for you.
I used to get pain in the arms that felt like it was the bones that hurt. And yes, unable to even move the upper arms due to the "sharp knife" sensation. I used to do all the painting in our home, including getting on scaffolding to reach 16' ceiling in the living room and the stairs leading to second floor. I removed ooogly (that's how we pronounced "ugly" for emphasis!) wallpaper from three rooms, skim coated the walls and then painted them. Yes, I was involved even with helping my husband install wallboard and learned to tape and apply the "mud"...took a while to achieve smooth finishes but all became better and better! I found it satisfying that I could do that type of work. That was all in my 20's to mid 50's....No way I could do any of that now! Actually, I had purchased paint and materials to do the kitchen and dining room just 2 weeks before I had that horrid fall onto concrete. Even though arm/hand-fingers/ are without high level pain now, no way that I would consider painting again. Those body parts will not be tested that's for sure! We are hiring a highly recommended painter to do the work. Serious balance issues that have evolved over the past 4 years is another reason not to climb onto ladders😱! Had to give up gardening and yard work also.

I am so sorry that you have such pain, especially when engaged in the work that you enjoy.
Perhaps you can update us if/when you do have the surgery? 🤔🌺