Seems like you do. If the doctors kept throwing him around like that then yes. I know, or at least partially know, what it's like to be thrown around, and if i knew someone close to me where dying i would spend as much time with them as possible.
Just know that he doesn't have to deal with it anymore. It's what we all though when a close family friend who, in a way, was like family, died painfully of lung cancer. For the last few months of his life he suffered no matter what they gave him, and couldn't swallow for the last 3 months of his life and hed to be fed by a tube. It was horrible, but thank some power that they don't have to suffer anymore.
I truly am sorry for your loss, but i think you should say something or talk to someone about what happened. If the doctor, or your dad knew that they had something wrong and said something to the doctor then they should have done something or looked into it.