Excellent question, although I am sorry to hear you and your kiddo are struggling with this. Here are my initial reactions to your inquiry:
(1) regarding discipline, you may want to elicit the assistance of a child therapist. I am quite confident that you have indeed tried many things with your son, but sometimes adjusting your perspective to move from a "consequence avoidance" method of behavior management (in other words, "Do it, or else!") to a "goal attainment" method of behavior management can really gain some traction and move your son in a different direction. Particularly for attention-seeking behaviors, really hitting the positive reinforcement angle rather than a discipline angle can help - and I know you are doing this too, but a therapist can point out chinks in the armor and help to fortify your strategies or reinforcement schedules.
(2) Given that you know little-to-nothing about your son's biological parents, it stands to reason that they may have had some emotional/psychological problems themselves, and passed the genetic vulnerability down to their child. With bipolarity in particular, these sort of mood swings and acting out behaviors are common. I would also advise having your kiddo evaluated for a possible medication intervention, as we may be able to curb many of these behaviors if we can straighten out (potentially) misfiring neurochemicals.
(3) And as with any situation that involves adoption, we look at the possibility of an attachment disorder. Technically called "Reactive Attachment Disorder," these are kiddos who have trouble with intimacy and emotional connection. Again, a therapist may be required to facilitate the bonding process, which grows more and more difficult as your child ages (in other words, the window opportunity begins to close). If this scenario is indeed the case, I would also recommend the book When Love is Not Enough: A Guide to Parenting Children with RAD, by XXXXX XXXXX.
I wish you well. These are some of the most challenging cases for child psychologists, so please shop around and find somebody with experience in this area, okay? If you are satisfied with the response, please hit "Accept." That is the only way I can receive credit for my answer. Thanks-