Everyone dies eventually, so the distinction in my mind isn't so much the how, though obviously does change, but the when.
If you take the stance that deciding to die is okay if you know you won't live past a certain time period, then you either need to arbitrarily definite a cut off time period for how long until death is certain a person can do this, or simply decide that anyone can do that whenever, because death is already certain given a sufficient time interval.
If you don't, then information that someone's death is imminent doesn't really change that.
Probably yes, however, I consider a person under such conditions to not truly be sound of mind, as torture is rather extreme duress, so that isnt really much of an argument in my view. I dont dispute that you could inflict an amount of suffering on me that would make me wish to die, I just think, while not in that state, that if I were in it would not be ethical for me to make that choice, and so that under that circumstance I shouldnt be able to.