Well first off, you'll never know unless you ask him. Secondly, I don't think at all that your dad decided to have a child with the intent of dying soon so that that child would have to experience the pain of losing him. Your dad just happened to be older than normal when he and your mother had you, and I'm willing to bet they take great pride and joy in you, and would never wish any harm or pain on you.
Death is a natural part of life that we al have to come to terms with on our own.Your dad may die when you're young, but then again you may not. I think it would really help you if you told him about your fears. I'm sure he can offer much more comfort than me or anyone else on the internet