From what I've read in the literature, TOS from accidents have better results from surgery than repetitve strain injury cases. The results are also better if it's done sooner rather than later.

The type of therapy you have had is similar I had initially, and while it helped restore range of motion, reduced pain, and got me better enough to do active PT, my ability to do anything was quite limited. I improved alot with the right kind of active PT, the edgelow protoccol. You can get it online www.edgelow.com and there are some tips I posted a week ago on how to learn it without a PT.

You have some differences from my injury and I'm not a surgeon so I don't know if this will help, but it's something you can try while you are deciding.

Two important things I learned what that TOS will not heal if you don't do aerobic exercise (which you might have to work up to slowly) and you don't strength the longus colli muscle in your neck.