Point taken. "Hydration" could be replaced with fluids, and the results could be reworded slightly: "...result in death from starvation", "...result in death from dehydration (thirst)", "...result in death from asphyxiation (lack of oxygen)".
Even if people don't get "asphyxiation", or even "oxygen", I think they'd figure out "death".
Yes. "Death" is a well understood word. Since we're talking about a living will, I think most people will quickly grasp that the subject is death. So, the document is really aimed at balancing comfort, longevity, manner and financial cost of death.
I'm against living wills. My recommendation is to have a trusted surrogate. People can fight the shifting sands of the death shysters better than pieces of paper.