Your Father needs to get a life, frankly. Any Christian who would fight with their grown child about going to church (as if that will somehow get them "saved") is not a Christian at all, and frankly is of the opposite persuasion whether they admit it or no. It's as simple as that. Sorry if that sounds callous, but that's the way I see it.
“Life’s journey is not to arrive at the grave safely in a well preserved body, but rather to skid in sideways, totally worn out, shouting ‘Holy ____…! What a ride!’” ~Hunter S. Thompson