hi, do you have power of attourney for personal welfare as well as personal property/assets? (they are 2 different things) and is it registered with the court of protection?
from what you say it sounds like your dad is conscious - does that mean he would be able to be asked what his views are and give a ratioonal answer? even by squeezing your hand if he cant talk (ie once for yes, twice for no)
the problem you will hve is that even if you do have the proper power of attourney in place and he HAS lost capacity, you will still only be abe to decide aboutthings that would have been offered to him, and it might be that feeding tube wouldnt be appropriate or offered to him even if he did have capacity. an analogy would be that he or you couldnt demand a heart bypass operation if it was neither appropriate or needed. Is he ia terminal illness situation? i only ask because previously i worked as a macmillan nurse, and relatives often asked about feeding as it is a really improtant part of life, and it was a very hard thing for relatives to let go of, even when it was completely inappropriate or unnecassary.