Here's what I would do: I don't think this is a chin problem, but a people problem that involves chins.
Whatever your normal relationship with your Dad is, I would put that aside for the sake of your chin. She needs you to step up and be more of a grown up than your Dad, adn that means finding out how your dad needs to hear it. He may just feel what your saying is normal kid stuff, he might have and ego and think he knows best. Which is kinda what it sounds like, but I wouldn't know for sure. I would do a ton of research and print off articles for him. Have it in a stack and ready to give it to him. Make sure you have a list for him of all the bad things that are happening when he's doing this:
1. He could break a rib and cause pneumothorax (punctured lung)
2. She will pee on him
3. She will become frightened of you and him
4. She needs six months to come around
5. She may never want to be held (just like some humans don't)
6. this kind of behaviour will cause fur slip, which is a sign of severe distress (and a defense mechanism, meaning they see him as danger)
7. they are prey animals and need time to build trust, and he's not helping.
I'm sure there's more which you can add.
Now, don't approach him with the knowledge that you know better. People don't respond to that, they get their backs up adn their ego gets in the way. MOst people don't want to be told what they're doing is wrong. So, ask in a very non-blaming way why he's doing what he's doing. He probably has a big theory and thinks he's helping. So, after he has his rant (let him talk himself out and ask lots of non-blaming questions) gently point out what you know, and provide articles and data. Ask him if he could kindly do the same for his theory. He can't, but don't tell him you know that. Just let him do the research. If he can't back it up, the ask him to stop. If he does find something, then you can find a better counter argument. AS someone who followed advice to do that to my Kira, I would't recommend it. She just needed a wheel, not torture.
This conversation is up to you, and how you approach him. Don't have attitude. You must leave all this behind for the sake of your chin. Check out this website
http://www.cnvc.org/ IT's about nonviolent communication, which is difficult. but there are ways to say what you need without upsetting the person you're expressing yourself to. the sentences they teach go: "when you _____, I feel ______" Ie. When you grab Amy I feel hurt and worried that she's going to be terrified." (don't add because you did __________) Maybe get your mom involved. She probably knows ways to win over your dad.
If this doesn't work I would suggest the family takes a trip to the vet with a secret call ahead of time to reprimand dad for his behavour. Some will do this, and if he doesn't listen to you, he will listen to someone with higher authority.
I also like the lock idea if all else fail.
good luck, I hope this helps! Keep us posted
