Hey Sarge, I don't know what you've been through, but I have a lot of chronic health problems, and like some of the other guys have said power tools really do help to ease the physical burden. I love hand tools too, but reserve them for finer work. If you go down that route you also need to have good dust control, and a decent dust mask as lots of bow woods have nasty dust. You don't want to add to your health problems with chest infections, and sinus trouble.
I guess you already know this, but pace yourself. Bowmaking takes a lot of concentration, especially tillering. It makes you tense, which is a problem if you have shoulder or back pain, or arthritis, your posture slumps and you get in the habit of working this way and it puts even more strain on the joints.
What do your physical therapists say about your arthritis and impingement? A good therapist should really be able to help with that, identify the cause and to relieve tension with exercise/therapy. Not all therapist are equal. I have been to some which are downright useless, to those which are a great help. Doctors seem to be good at treating the symptoms, but not always so good at identifying the cause of the symptom and really addressing the cause.
I wish you luck, never give up when you have a bad day, but do give yourself at break at these times. Its all about waiting out the storm, until you have a good day.
Hamish