I am working in the UK, I have not examined you, I cannot provide medical advice over the internet. I will use at times vague wording mainly because we cannot be sure which person will be the 85% that are happy, the 10% that are less happy or the 5% that are worse following their surgery. I think the system is different in the US in that here we would err on the side of caution due to not having as much capacity and also not being able to run from our complications as easily.
I have been putting in shoulder replacements for the past 6 months as part of my training. I take about 1h30 mins from the patient being positioned until I am ready to move the patient off the table, anaesthetic time is variable. My trainer who is doing most of the replacements in this region can perform it in around an hour which is the general standard here. The risks I consent for include: pain, bleeding, infection, damage to nerves and tendons, stiffness, swelling, dislocation, reoperation, implant failure due to loosening or wear, revision, fracture, clots in the legs and or lungs, heart attacks, strokes, amputation and death. We usually keep patients in for a day or two following the surgery for optimising analgesia and ensuring they are safe to be returned home.
The amount of strength and mobility following this surgery cannot be guaranteed, the main benefit will be the pain relief. If you don't have pain you have the risk of being dissatisfied that your painless joint has been replaced with an imitation joint often that is a bit clunkier/warmer/more swollen than it was before. Most of the patients take 1yr to reach the full potential of the shoulder, usually it takes about 8-12 weeks for people to start driving again and tackle most household chores. Most of the time we are doing these replacements for cuff arthropathy - people that have torn the cuff, the shoulder joint has worn and now they are struggling to cope with their pain/immobility. The often given advice is to expect to be satisfied with doing activities at the waist level, it is quite likely you will be able to do things up to the level of the shoulder, don't bank on doing things above your head, internally rotating the shoulder to reach between your shoulder blades is usually lost but most don't have that to begin with. We advise against loading the shoulder such as using it to push down when rising from a chair or using it to carry out DIY. I'd be quite taken hesitant if you wanted to push your ST1300 around with it.
Infected joint replacements are fairly uncommon but when it does happen it is a pretty big nightmare that can lead to many more operations, many months on antibiotics and the possibility of a constant smouldering infection that never truly goes away. Infection can be from the surgery itself or many years later if bacteria reach it through the blood from a chest infection, water infection or other seemingly inconsequential illness or minor injury. The other thing I haven't seen mentioned much is that the implant will wear out or loosen in time leading to failure, current data suggests implant survival is 10-15 years. There is no current revision option for a reverse shoulder replacement that I'm aware of, once the joint is worn that will be it in terms of operative management.
From my small experience and from what you have described I can't imagine you would be guaranteed to improve much with a shoulder replacement. There is a risk of making things worse, you will likely trade some of your mobility and not be guaranteed your strength. If you leave the shoulder as is the worst outcome will be gradual onset of arthritis in the shoulder which will bring pain and a reduction of movement. The treatment for that would be a reverse TSR.
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