You're not alone... when I was little my mother had made me her surrogate husband. It was a very sick relationship and she actually had me hating my father when I was growing up.
It wasn't until I moved out and went to college that I began to realize how screwed up my family was. I started staying with friends and their families for various holidays and saw what healthy families do and how they interact. The rage just got worse and worse.
When I finally wrote "THE LETTER" and sent it, my mother went to her grave never speaking to me again. My father on the other hand, wrote me a letter (which I know was very hard for him because he was never a verbal type of person - especially when it came to expressing his emotions) telling me how sorry he was for being absent in my life and how he wanted to make it up to me. I was so glad that we were able to reconcile and form some sort of bond before he died.
So, I would suggest that you take the time and enjoy your dad while you can. All it takes sometimes is for someone to bend just a little (in our cases our dads) and a whole new world of communication opens up and healing can take place.
There are no unresolved issues - they just didn't resolve themselves the way we would have liked. "Grinder and Bandler - Neuro-Linguistic Programming"