I'm sorry you're going through this. It's tough to realize we have the answer they need, but they don't want to accept it.

Keep praying for him. It's the work of the Holy Spirit to change your dad's heart and mind. You've done your part. You're still loving on him, and he knows where that love comes from.

Never give up. I recently experienced this, and in the end, God gave me peace to let the outcome rest with Him. Even in the final second of life here.