Dyslexic 50+ year old here so I went through the sstem being called lazy.
OK it will probably always take your DS longer to complete reading and writing tasks but he will get faster.
Does he have coloured overlays? They were a game changer for me.
I would also suggest a Kindle (not the fire), not cheap but you can get all the classic books free from various places. You can set it up with a dyslexia friendly font and change the text size and layout so your ds isn't faced with a 'wall' of text.
I'd suggest getting him to learn to touch type, there are loads of free 'learn to type' apps.
Has he tried using a tablet with hand writing recognition?
One thing I will say is don't prioritise written work over art and practical subjects.
Being dyslexic is tyring, being able to make something, either from crafts or meccano or electronics is fabulous, it's somethign you can do, do well and achieve in.
Experiment with producing work in different formats eg he might struggle to write a page about subject X, but he might be able to do a power point and present the information to camera. A documentary on the wildlife in your garden / local park filmed on a phone may have all the content needed.
Make sure he is learning, let him explore the way he learns, what works for him and what doesn't. Get him to keep a diary of his dyslexia (not necessarily a written oine), it does vary, some days I just canot read, and I love reading, but I will read the same page 3 times and not retained anything.
There is a company that employs architects who are dyslexic, and only ones who are dyslexic, the company finds it cheaper to emply other people to write the reports but let the dyslexics do the actual designing bewcause the designs work.
I got an electronics kit at about your son's age, it was the best present I ever had and in montyhs I had built a radio, wired up an alarm for my bedroom (sound or light so I could read after hours) and various other projects.
Dyslexia is as much a gift as a difficulty, we excell in certain areas, but we are ready for new technology and often we are the ones designing it.
Have you been watching the Jamie Oliver cooking series? He cooked a fabulous cake for his daughter's birthday, but had misspelled the bunting. I believe he dictates his cookery books.
As for languages, I and a couple of other dyslexics, on my uni course picked up BSL easily. There is no written component, it has a logic to it that just makes sense to dyslexics and a GCSE is being developed.
Good luck to you and your ds.