Dawg,
I don't understand because I've never been shunned even though it will happen one day if I'm Df'd and my in-laws are still Jdubs. I cannot really understand the whole concept of shunning period especially your own flesh and blood. To me it is a lot of BS and nothing more.
You can work on the more subtle things like some mentioned previously such as send a post card or a phone call, hope he answers and blurt a few words out. I don't have the answers you are looking for but don't give up. After all he is your father and that's all you are asking him to be.
I know it is indeed frustrating. I went without speaking to my father for 25 years, not for religious reasons. And another family member helped us to reconnect and we currently have a channell of communication even if it isn't as father and son as I would like it to be it is still comminication.
Dawg, I hope you the best in whatever decision you make!
Quirky1