Wheather you stop the feeding tube or not, you should call in hospice. You should really do it, now. This is what they are here for. To help familys at the end time.
I think that what ever you do, that it's an extremely personal and family decision for you to make. We all have to come to grips with the grieving process in our own ways. And, how much time it takes and how we handle it, either makes us or breaks us as an individual.
It is my sincere hope that your family can find peace. All you can do is to love him. And, know that he always loved you. If you can put yourself in his shoes and say, "What would he do, what would he want, if it were me?". Then I think that this might help you find some answers that you seek.
You are in my prayers,