CAmom,
WOW, my oldest difficult child and your difficult child sure have Alot in commen. Mine was always told if he ever turned his negative mindset into a positive one that "The sky is the limit".
Mine is Highly manipulative, cunning, socially on cue, very clever young man with remarkable verbal skills, though like yours, his academic efforts did not match. That is, after I released him to his own efforts around 7th/8th grade, he began to fail or fall behind and also began to use. Before that, I needed him to make A's and B's only. I find that much of who I wanted mine to be was about me not him. Mine is doing quite well without dad and I in his life now.
I think it's a really good idea to let them own their relationship with their PO's too without our interference. Saving them from consequences has only made things worse for mine.
In any event, I think you have been holding up really well under the kind of emotional manipulation card your difficult child has tried to play in the past, or recently. It is SO hard to not buy into it, we want so desperately to feel that bond, you have my sympathies as to the heartache.
Stay strong...you can do it, it's good for difficult child too, really. Long run payoffs. I wish I had "caught on" sooner...SO much sooner.
With care,
lovemysons