No, you are not being unreasonable. You love your dad and you want him to be healthy. But you can only do so much. If he doesn't have the desire no matter what you do or say won't make a bit of difference.
You've tried but now it's time to let go. He will do what he wants and that's that.
I think you were being a great daughter by trying to help him.....he just doesn't want it.