Since you're overseas, I would focus on teaching him executive functioning skills. You can order a book, I like Ann dolin's homework made simple. She runs a business in the dc area and maybe she'd consider skype sessions if you can't find a local tutor.
There are many things you can implement yourself and since your child is older and seems bright get his input in developing systems about homework/classroom strategies. CHADD does lots of webinars. You may want to contact the local chapter of the international dyslexia association:
https://dyslexiaida.org/in-your-area-with-global-partners/ Even if your kid isn't dyslexic, language based LDs like dysgraphia and ADHD have a lot of overlap as to effect strategies.
I would re-investigate medication. Reconsider the usefulness of CBT unless he really likes it. Boarding school seems a little drastic. That might prove more anxiety inducing. Also in terms of interests, lots of kids just naturally grow out of things like legos. Wanting to sit and veg seems pretty typical of pubescent kids. In terms of IEP strategies, he should start to have a say. There's more than one way to skin an apple, so there maybe supports that don't make him feel as self conscious.