Oh, good. I don't need to tell you that you've got a complicated fact pattern on your hands. And I'm sorry for your loss.
The answer to the whole thing might
(helfino, but it's possible) depend on where the matter is venued. Probate is state law and so is med mal, but the crossing of state lines with potential claims in more than one state means that Federal jurisdiction could apply (and with a wrongful death case, I'd say you've hit the jurisdictional minimal requirement). But even with a Fed case, there will likely have to be some choice of law considerations. It's a tangle for your lawyers and it'll be a tangle for the judge(s) as well.
It's been over 25 years since I last practiced, so my word on this isn't great. In all honesty, it's as complicated as a Bar Exam question.