Very quickly about your shoulders as I could go on at length about training and injuries. Even if you have torn labrums there are exercises you can do for the rest of your body. Core strength, legs, cardiovascular system, stretching/agility etc. All will help if the goal is to continue sailing.
I am no expert on your condition, but strengthening all the different muscles around the shoulder joint would be something I wanted to look real hard on. I would want my supporting muscles to offload the labrum so I could function as close to 100% as possible. Your fysio therapist should know how to do it. Sounds like you have been hanging on/doing stuff directly off the joint/skeleton and not the supporting muscles.
I have had several injuries of various severity. I find that if I dont work out my injuries actually become worse. When I work out, I dont notice them much after the first weeks. I have 60 more years of working out to do..
Please stay active, dont give in to age!

Your beams are quite heavy compared to your all up weight. Did you do the engineering yourself, or was the design a case of experience and some guesswork? I am sure they will work well for your application. If I was to do wooden beams, I would use strip planking with carbon inside and out. I would also vary the dimensional section but it is not likely to happen now so it is just fantasy.

I would like to see more pictures on how you fitted the trampoline if you have some. How did you do the foils and daggerboard wells btw? I am asking as there is always something to learn.