The basic process for transferring to Medicare is that you and the work comp insurance company do an estimate of what your future medical costs are likely to be under Medicare, an MSA, and then you close your work comp case. At that point, Medicare reviews the estimate and decides if it will be accepted. If the estimate is too low, you can end up in a situation where Medicare will not sign off on the deal so you can not get Medicare coverage but you no longer have work comp coverage because you closed your work comp case. So the estimate needs to be done correctly. medications in particular are complicated because Medicare D. doesn't cover very much. I'm not quite sure how to set it up properly to cover medications but I think it is in fact possible.

The MSA only covers what Medicare covers. Medicare does not cover or co-pays for Medicare, I believe that has to be separately negotiated.

Medicare plus Medigap covers
1) a small amount of medications
2) trigger point injections
3) surgery
4) MRIs and other diagnostic tests if clinically indicated.
5) physical therapy that can be shown to produce functional gains, physical therapy/massage therapy for pain relief is not covered. There is a cap on physical therapy as you mentioned. You can get somewhat more physical therapy if you are getting it at an outpatient clinic attached to a hospital, but still there are limits.
6) Pain psychology is covered I think up to 30 visits a year, probably also with the requirement that you are getting gains.
7) I think certain kinds of nerve blocks are covered, but I'm not sure which.

If you are very poor, you might qualify for some attendant care through another government program.