if the Jehovah Witnesses come to your door randomly what would your response be
It would depend on the circumstances and the people involved. Some of them are very nice, and quite open. I studied for two years with one like that; it was my introduction to the Bible. The one thing I couldn't swallow was Jesus not being God, however, and eventually I left off.
The last time JWs came to my door, I engaged them there, and did not let them in as they wanted. The lead guy was a higher-up who regularly gives speeches at their conventions. Yet he couldn't get to first base with me because I know the Word too well. The other guy was a mature adult, but new to knocking doors and probably to the religion as well, since the two are almost synonymous. When it was all over, the lead guy virtually stormed off in defeat, but the neophyte turned to me with a big smile, and extended his hand, which I warmly took. I felt really good about the whole thing. I had engaged them on my own terms, and brought their false arguments to nothing.
Before them, there was a young man handing out literature in a parking lot. I engaged him for about two minutes and went for the big issues. As I turned for the store, I glanced back - and saw him packing it in and getting in his car to leave.
I would point out to your dad that the canned questions at the bottom of their articles and books are no way to study the Bible. People need to search things out and ask their own questions. What's important to one may not be to the next. That's how we grow, not by rote indoctrination. I would prefer youtube videos to their method of studying. Or maybe your family could have its own studies, or someone's church would start one in their home.