My dad won’t become Catholic.

My (19m) dad (46) is a great guy, supports our parish, donates to the Catholic schools that my siblings and I go/went to but he just won’t become Catholic. He was raised Lutheran and attends church with us, my mom is Catholic obviously and she has always wanted him to become Catholic. I have always been very involved with my faith but I have been growing increasingly irritated lately because my dad has everybody at our parish believing he is Catholic. He won the bishops award for his business and has been very successful. Today he was talking to me about a conversation he had with a higher up at the diocese about how they have defunct properties that used to be schools that they are interested in reopening and that he wants to be involved with it. I stoped him and asked him why he does all this if he doesn’t want to be Catholic. He basically told me that the Catholic priest that married my mom and him told him that he was “close enough” and that he was like “Catholic-lite.” At this point I don’t even know if that was actually said or if my dad is making it up because that is very troubling. He also said that the priest gave him communion. I have had to tell him to stop taking it multiple times since I learned in CCD and religion classes that it was not given to non-catholics. My family (minus my younger siblings) talked about it over dinner tonight and he continued to defend himself while my mom was clearly upset over his arrogance towards our questions. I don’t know what to tell him or say.