My eldest ds was not dry at night at 11 or thereabouts. He had been dry at night for some years, but went backwards at about your ds's age, @Luna28 - and like you, we tried everything, including the hormones (Desmopressin) if he was having a sleepover or on a trip).
One thing that did help us was lifting him for a last wee at around 11pm-midnight. I know it's not what the experts recommend, but by lifting him, we managed to make the problem much more bearable - it went from every night to half the nights of the week, or a bit less.
We tried the alarm early on in the problem years, but without much success, but tried it again when he was about 11, and it did work then. I am guessing it worked because he was ready for it to work, so I would advise you to keep on trying it periodically - if you haven't tried it for a year, it might be worth another go.
Ds1 got over it in the end, and I am sure your ds will too - but I can remember how worrying and frustrating it is, so you have my sympathy.