Hi Hiccup, When i first began to study with the witnesses. The things i was learning put me on a high. I felt like a window had opened up in my life and saw things in a completely different way.
One of the things that changed for me was my outlook on material possessions and my view of money. Originally from Ireland i moved to London . I had my own flat and a fairly well paid job. That was the only thing that was keeping me there at the time. But once my studies began, all that changed. I no longer felt "materialistic", didnt feel i had to be living and working in london etc. So i decided to move back to Ireland and "yes" i became a window cleaner.
The reason for this was a lot of other witnesses were doing similiar work and it freed them up to go out on into the "field ministry".This of course impressed me and i was of course so zealous ( on an emotional high) at the time that i decided to do the same.
Your father is probably following a similiar pattern. I could be wrong of course , but it might be a factor. He might be on a high at the moment because of his studies and is perhaps impressed with others at the KH and simply following their example.
Also the fact that emphasis in their teaching puts the kingdom first and material things second.
I hope this helps. But please tread carefully as others have mentioned on this tread. As your father will view it that satan is trying to use members of his own household to put him off the"truth".
I hope things work out for you. But no matter what happens in the future, he will always be your father and will always love you and your sister.That i can assure you will never change.