Ok so he can heal that's confirmed. But now the thing is let's say he completely heals his gramps which i think might be possible it doesn't change the fact that he is old and doesn't have much time left. Snake already checked he has little time left and i belive that is not concerning the sickness. So i belive he can heal him but he can't extend his life.
Aaa i knew the end was coming no.mote silly. I want more of them