The only thing that makes me think that this person isn't an experienced criminal is the phone.
That phone should/would have been thrown out immediately. The fact that it remained on throughout the hour long drive...and even into the next day...says that the perp may have forgotten that detail. But, if we're talking about an experienced criminal, then--as Doc suggested--he may have left it on to throw people off...to take them in another direction entirely.
I think we're dealing with a young adult as well...someone at least 18 or older...someone with a record, but not necessarily a sexual offense. Burglary, gun charges, something that takes planning, something that's gutsy. I agree with you that a teenager would have been talking by now. That MAY explain some of the tips they've been getting...maybe one of them was a teen. But the 'ring leader' was, most likely, an adult who has managed to keep the others quiet for a decent amount of time.
On Doc's early discussion of the phone location, I'm really torn. On one hand, I think the perp didn't realize she had the phone until an hour into the trip...and then threw it out the window or placed it somewhere alongside the road. On the other hand, if that phone isn't on her body or on his property, I don't see how they tie anyone to the phone. If they find it in the national forest, for example, that doesn't do anything to lead us to Brittanee or her killer/abductor. I'm praying that LE has been saying that the phone is important because they have been given information that tells them that Brittanee is with the phone.
I wonder what happened in early December to make someone start talking. Wonder if we could find arrests in Georgetown for that time period.