Is it possible to just get my MSA in full if I relieve all parties of obligation?

No, not unless they all agree to it. However, Medicare is not likely to do that. If you are getting yearly lump sums and you are not using them in the calendar year you are given it, usually, you are free to spend it on whatever you like. For the rest of the monies, you have to stick to the agreement, unless Medicare agrees otherwise. Talk to the lawyer you had. If you didn't have one, either get one familiar with MSA's or talk to the people you settled with. Good luck.