FWIW, my grandfather always disliked my father and made it obvious. He made lots of remarks about him not being good enough for my mum.
Oh his death bed, my father went to visit him. For various reasons my Mum couldn't go. He apologised and said how he'd be so impressed with my father and how he'd misjudged him and he was glad he made my Mum happy.
But it took 20years of marriage for him to do that. Though it has to be said that my Mum's relationship with her Dad wasn't great for a lot of reasons; divorce, living abroad, just generally never very close and she didn't live with him during her teens.
I think you have to reassure your Dad that he's still no1 in your life somehow (even if hes not) and give him time to come round to your choice in time. If he won't invite your DP round, invite your DF to things with both you and your DP. It might be worth biting the bullet and accepting your Dad's way on his patch to an extent because it maintains your relationship and he gets to see you have grown up and are an adult, otherwise he'll forever see you as his little girl.
If you invite your father to do things with your DP on your terms, it makes it more difficult for him to refuse, as you are inviting him to be part of your world. If he feeling less important to you, he's more likely to be pleased by being asked to be involved by you. If he refuses, you have a stronger case to say to him that you want him to be part of your life and its his choice as to what he wants ultimately. Rather than you being the 'difficult' one in refusing to do things on his terms on his patch.
Remember its a marathon not a sprint.