I have similar issues. Hunted all over with bow and a few years ago my shoulder started bothering me so bad I could hardly lift my arm. This went on and off for several years. I was back and forth to the Drs. and they kept telling me it was bercitis (sp). I told them BS...but what do I know....I'm just a lowly 'ol civilian. Well, it got so bad I couldn't even sleep. Finally got a Dr. to listen when I went in to get my broken leg looked at (fell putting up a treestand)

Anyways, they did a CAT scan and found 3 things, a SLAP tear, Rotator cuff tear, andsomething to do with the socket being bad and my shoulder poping out of place. Hopefully going to get it all fixed this winter. I sure as hell am not getting it done til after season.
Well, I went in and got my crossbow permit and have been using it for the last couple of years. I still enjoy hunting the archery season but will say that it doesn't have the same "thrill" as shooting a conventional bow. Nothing wrong with that....I am just sort of a thril seeker type and like the rush of old school hunting.
I picked up a Horton for a decent price and it shoots good. I looked at several different ones and it all came down to money for me. Couple of CONS I will mention.....They are noisier than a regular but can be quieted somewhat by limbsavers and such. The other issue is that they are HEAVY!! I am right handed...so have to hold it up with my left arm...this is the arm that has the shoulder issue. It is pretty hard to hold it for any length of time. I would suggest you try and find one that isn't heavy. I maybe should reinterate...it is FRONT-END heavy...not really heavy overall. They are also a little ackward to get used at first do to being "cross"bow, as in the bow sits sideways.
Pertaining to your question on bolts....The brand you end up with will have a recommendation as to what shaft size they recommend you use. I have been shooting archery for many years and have hundreds of old shafts laying around. If I remember correctly 2219's are/were to common size if you want to use aluminum.
Finding places that have a variety of different types to look at/try out can be frustrating. Not sure where you live but Cabela's, Bass Pro, and Gander Mountain sometimes have decent selections to look at.
Good Luck and let us know what you decide to get.
WW