First suggestion...never put personal information again on Facebook. It's a public social network that anyone can see, even if they don't have your password and member name.
Also if you really don't want to be DF'd, lie like a rug and tell your dad that someone hacked your account on Facebook and wrote that there to get you in trouble or that it was a bad joke, if you have a really odd sense of humor.
Be convincing. But, they lie to you all the time, why not lie back at them? They don't have the truth, they use your words against you so they don't deserve to be told the truth.
They justify lying to authorities about JW activities with that same reasoning so turn it around on them.