Not an easy situation. Part of me would be telling me to take my boyfriend to my parents house and knock on the door. Let your partner see first hand what would happen.
I would most certainly be upfront and open with his family about your upbringing and show them from the watchtower articles why and how you find yourself in this situation.
The internet is a wonderful source of information and there are plenty of stories matching yours that they could see for themselves that you are a victim.
Good luck.