Ds1 (16.8) has ADHD. He was diagnosed at 8 years and I quickly realised that I too have ADD. A trial of medication was very successful and he continues on a long acting dose daily. Once he has finished all his exams (this time next year) the plan is to start reducing his dose to see how he gets on although he is not all that keen to stop taking them as he feels a real benefit.
He is very academically able but lack of concentration and motivation stop him reaching his true potential at the moment. I was the same but once I went to college to do something I was really interested in I "shone" and I'm sure he will be the same. Ds plays a musical instrument very well and plays in 4 different orchestras. Again with a bit more motivation he could really be so good - but hey. He did well in his standard grades last year and is doing highers atm. He is expected to do ok.
He was not good at making friends in primary school and struggled with relationships but now has a big group of (like minded) friends. He has had several girlfriends and seems popular with peers and teachers!
He is easily annoyed by things that his brothers would take in their stride but, where once this would have resulted in a meltdown, he has now worked out strategies to cope.
He is generally a polite, helpful and friendly (if somewhat unusual) lad. Friends and complete strangers often comment on his lovely nature.
When he was diagnosed I was shocked and saddened that the future seemed less than bright for my lovely boy. My dh, like yours, took a long time to come to terms with the diagnosis and it's only recently that he has started telling people.
So - as you can see, with help now in place, the future is very bright. I don't doubt that, as a family, you will be able to work through the problems. I haven't grown out of my ADD but have a responsible job, in a senior position and have certainly learnt to manage it as I'm sure my ds (and yours) will too.
I am just going upstairs to renovate his bedroom. It looks as if we have been burgled but you can't have everything. 
All the best to you all.