I would have so many questions to ask you if we were sitting down together. But I am comfortable recommending keeping the arm slightly elevated as tolerated (maybe just shoulder height/slightly lower at first) and gently squeezing a stress ball anytime you are sitting down. Maybe for a little while before going to sleep. Keep it low intensity and slow, one squeeze every 10 seconds at first. Progress as tolerated. Stop if you feel anything doesn’t seem right or any pain. Build up how long you are doing this over time. Start with maybe 2 to 5 minutes a day. Add a minute or another round of squeezes every few days. If it seems to be helping, resist the urge to amp it up too quickly.
I would still recommend telling your surgeon/doctor that you are going to try this. Just in case they have an objection.