Flower,
Do you feel that your father is a weak pawn in all this, and that your mom rides on the back of his good will? It may be that your father has been under her thumb so long he can’t see it, and he feels in the middle. It sounds as if you don’t hold him fully accountable. That he doesn’t fit in the same category as your mom, but ends up being her accessory in crime.
What you might do, if you want to gently prod at him to perhaps look a little deeper at your feelings, and give him time to think about it more, is slip the card into a larger envelop with a note. The note might say: that although you are happy to receive a card from him, you feel (fear?) it is yet another ruse of your mother’s, and that you can not risk this intrusion, as you have found that not interacting with her has been a tremendous relief in your life. Tell him you realize that maybe he does feel caught in the middle, but you have to make a stand for yourself. Educate him. You know for yourself, your understanding of your Nmom was a slow unfolding and unpeeling of a false reality, and it is probably so for your father as well. With many more years invested. That way you send the card back, in kindness, as well as a point made. Good luck.