Brother, you can't tell it yourself but from how it looks to us from here is you're creeping the girl out and his dad. And the girl seems to be enjoying it or doing it out of spite because of your behavior and to make you jealous or maybe she just doesn't like you.
This is not even about Islam. This is about girls and i can tell you the way you're acting, you're giving her all the control. She doesn't have any respect for you and your continued obsession with her is making it even easier for her to toy with you.
You have zero chance of getting this girl to like you, don't even think about marriage especially the way you're acting around her. If you were even to get married to her by somehow forcing her father, you would regret it the first night because if a girl doesn't like you, she can make your life a living hell. With your current behavior, you're only repelling her away you know like the same sides of magnets and the magnets are getting stronger(your behavior) so the repelling is getting stronger =)
Here's a story from my own life.
Some years back where i was studying, there was this girl who really liked me. And back then, i really wasn't interested in girls...had other priorities in life etc. I was always nice but acted like i didn't know what was up. And she would try to talk to me and generally do things that show her likeness for me (i don't want to go into that now) and the strange thing is, the more she tried, the less interested i became. It wasn't that she wasn't attractive - by all means she was and one of my friend tried really to marry her and she eventually got married to him - but i didn't have to work for her affection, her liking and that somehow made me less interested. If it was now, i probably would have tried to hit on her first before she had a chance lol.
So the point is to her, you're the girl in my story but worse...you're creeping her out. Questioning her, talking to her father....take a step back and look at your behavior. Does it feel okay to you? She and her family might even feel threatened and be scared of you.
How would you feel if someone else was doing that to your sister? Yep, that's how her family is feeling.