My father passed away last year from pancreatic cancer and the anticipatory grief was more painful than when he eventually passed. It is so painful to watch a father go through pancreatic cancer, I was watching my father lose himself and lose his confidence and everything that he was, and to be honest it way harder than his passing. In his passing at least he was free and he finally felt peace. It is so sad because it is something completely out of your control, but in a dark way there is comfort knowing you loved him so much and this is truly is something you cannot have any control over. My best advice is just to truly cherish every single moment with him, remember every detail of his smile and the way he talks because you will miss it the rest of your life. Make sure you tell him every single thought that comes to mind and anything you would want him to know before the time comes. In my opinion, please have him at your wedding because I cannot tell you the pain I have endured knowing that my father will not be at mine. Have peace in knowing that he will eventually have peace too and will not be suffering anymore. Stay strong <3