You are in your early 30's and you're growing up - taking responsibility for yourself. That's a good and natural thing to do.
This isn't the first time that a parent and child don't see eye-to-eye on something (it could be politics, racism, legalization of drugs, women's rights, freedom of speech, choice of spouse, raising children, career decisions, immigration laws, the environment....or religion).
Accept this fact and be respectful. Being a faithful Witness is obviously very important to your dad. And, like any good dad, he wants the best for his children (this means all in his family must be faithful the the Organization ... because the alternative in his mind means eternal death).
Live and let live. Move on. Be good. Be free.
ginger