PS I am sure you have wondered about this and I have no idea if it is correct, at all, but here is some further info.
www.schizophrenia.com/earlysigns.htm#
The thing to remember with whatever is causing your son these problems is that finding out what it is, and what will help him, is the goal. Not avoiding labels etc. I personally think labels are only unhelpful if they are untrue.
I'd also explore PDA and something else called ODD (Opposition Defiance Disorder) and ADHD, all of which we considered for our DD - who is diffiuclt but no where near as difficult as your son. In the end we went through CAMBS and all we were told about our dd is that she has autistic tendencies. Her behavior was not as extreme as your son at all and she has, as she got older, got a lot better; although hormones are now creeping/deluging in! She is almost the same age as your son.
I've tried to parent in a different way and have found 'Supernanny' doesn't work for us! But I really feel this is nothing at all to do with your parenting and there must be a medical or other underlying issue.
Is there any chance he suffered some trauma or abuse anywhere in the past that could be affecting him? The reason i ask if because I am an adopter and as we do not know about our children's full background (it's actually my son who is adopted and he is pretty much fine) but adoption makes you think about all these issues, and connections to past experiences etc. Normally if you have a birth child you do know what has happened in their lives, but not always.
Your son's behavior and his anger to you seem to me (IMHO) to kind of be pushing you away, making it impossible for you to love him, or at least trying to do that. I am wondering what is driving him to this. If the behavior and attitude are relentless (always the same and never any let up) I wonder if that would point to a medical problem, imbalances in hormones or whatever or in the brain that make it just so very hard for him to react normally to things like a fun day out.
In your shoes I would be thinking about these more extreme things and not allowing anyone to suggest it is bad parenting etc (which I had suggested to me, as in not strict enough with dd!).
My friend's son has anxiety and some sort of Obsessive Compulsive Disorder (OCD) and she has been told it is her parenting (it is not!).
I had OCD in my teens and 20s and anxiety in my thirties. When I look at my family history I can see in my dad's side of the family anxiety etc was very present.
Some might see it as learned behavior but I do think there is a genetic propensity for some mental health issues as well as the 'learned behavior thing'.
Are there mental health issues in you or your son's father's wider family?
I was lucky in that I had talking therapies (Cognitive Behavioral Therapy) for my anxiety and it worked brilliantly. I never had any treatment for OCD and it morphed into an eating disorder I am still trying to be free from, and seeing some success with (yes) more therapy!
I guess I am telling you all this to say that I know something about the topic of mental health! BUT I really think you need the best medical brains in action here, I tried to read all your posts but could not easily see what doctors had been involved in his assistance.
Please be careful how much you share any ideas of problems with your son. You do not want him to label himself if it is not true! It is very easy now for kids to access all kind of information and I think it could be detrimental to him if he got hold of some old-fashioned ideas of schizophrenia or other mental health issues which may not be helpful.
School are about education, and I don't think this is an education issue. It is affecting education but I am not sure you or the school can 'teach' this out of him! He needs more.
I wish you all the very best and really hope whatever is causing these issues your son can be helped and so can you. You completely and absolutely deserve help and to be free of this and he, although he may not be very likable or lovable at the moment, deserves this help too.