My first marriage of 23 years ended in a divorce after we drifted apart. I remarried six months later to a woman I actually met here on the DIS (completely unexpectedly). My DD was 20 at the time and initially took it well, but has never truly accepted my wife. She isn't openly hostile, but just avoids her whenever possible and just puts up a shield when she's around her. My wife initially made multiple sincere overtures to her but they were all ignored. When it's just my DD and me, she acts normally for the most part, but when my wife is around, she makes herself scarce. My DD lives about 60 minutes away and now I really don't see her often. I have tried to talk to her about it, but she refuses to open up. She is of course much closer to her mother than to me and communicates with her much more. My wife and I have discussed it and we realize that now, over 3 years later, my DD will likely never come around.
So I guess I've been put in a similar situation, almost being forced to choose between my DD and my wife...which is a horrible choice to have to make. But in the end, a husband and wife (legally or otherwise) need to make each other their top priority no matter what. Children grow up and go on to lead their own lives. We give them the best guidance we can, but can't live their lives or make their choices for them. My wife does not come in second to anyone. I will accept any consequences, even profoundly sad ones, that may come from that. May not like it, but I will never compromise my relationship with my wife.
Long story short, I'm having difficulty believing he's as invested in the relationship as you are since he seems to be siding with his daughter; when his loyalty and love should be with you first and foremost. I agree a heart-to-heart talk may be indicated as other posters have suggested. Raw feelings may be exposed and possibly hurt, but you deserve to know what's really going on here. JMO.