Before I was diagnosed with
Ehlers-Danlos Syndrome vascular type the doctors suspected I had marfan syndrome because they are pretty similar with being connective tissue disorders and have similar physical characteristics so I could give you my thoughts.
First I'm 26 now and was diagnosed only 4 years ago and honestly I'm very happy I didn't know until then. I had my shoulder dislocate 5 times during my HS years which was probably the biggest result of the disorder up to that point so I was lucky in a way it wasn't worse. But not knowing I had the disorder, treatment for the dislocation wasn't tailored to my needs and I even had surgery which probably was a bad idea knowing now that I have a connective tissue problem. Anyhow since then I've had multiple arterial problems in my carotid arteries which put me in the hospital for weeks while they tried to figure out the cause but now that I'm diagnosed with the syndrome treatments for problems are quicker. While knowing the cause has probably saved my life (better/quicker treatments) it creates a great deal of fear now too and I would hate to have had to deal with that as a child...
Medical advances are pretty good now and getting better, if you can find specialists and quality hospitals to be treated and monitored in it really helps but since it is genetic I doubt there will be a 'cure' in his lifetime. Personally I wrestle with the idea of reproducing now that I know there is a 50/50 chance of passing this defect on to my kids and I probably won't or I will do gene screening to avoid it but since you already have the kid your only choice is to accept it and move on.
I'd say find the best possible doctors and the nicest hospital, do research and move if necessary cause like you've found you will probably spend a good chunk of time there. I'd also say to try and let the kid lead as normal a life as possible, avoid causing him to fear his own body as he grows. If thats possible I've no idea.