First I want to say to you, Cognisonance, you're a good egg for caring for your JW father.(I'm assuming this part is TRUE? or perhaps your MOM)
Anyway, someone you love has a biased opinion on all (JW)spiritual things. He is elderly. He probably will not change his views, so late in life. Accepting that, you can find a way to be able to respect his beliefs and respect him as your Father. There are no simple answers.
I do not like to lie to anyone. I do not like when other people try to manipulate and control me. Having said that, sometimes in order to avoid stress and tension and disagreement, you just concede. Who does it harm if you concede. Just love him, anyway. Make your peace.
He believes what he believes. You believe what you believe. You don't have to tell him you watched a certain movie or that you just purchased an antique.
I hope this helped you a little.