"Concessions we're willing to make (and already have made) are not telling him who he can/cannot hang out with, not forcing him to check in and get permission to move around"
Hmmmm, I always tried to made it a point to know who my difficult child was hanging out with to include getting confirmation from other parents about transportation and where the kiddos would be etc. Also asked that my difficult child please let me know of any changes in the plans. A parent cannot be everywhere to babysit their kids nor do I think they should so long as they have no reason to think that their kids are doing anything wrong. I might be wrong but it seems that in my case things started going wrong when I started letting loose a little bit. All it takes is for them to get with the wrong group of kids. I obviously did not know this new girl in the neighborhood as well as I thought I did and she was the one that introduced a heavy drug using group of kids to my difficult child.