A few thoughts..
First you might just give him a few more years, he is still quite young. I know it doesn't seem like that to you now. There are many aspects to reading. My DS14 taught himself to read at 3. But at 5-7 didn't really like to read fiction/chapter books. Emotionally & socially he wasn't interested in those books. He mostly read non-fiction science books. IMO it's not uncommon for kids to pick stuff up in a non-linear fashion. READ to him books 2-3 yrs about his reading level, find well written books. Experiment with what he likes to read, as I said at this age my son mostly read non-fiction. Most early reading books are boring & uninspiring and not even that challenging to read.
As for specific exercises that would depend on the type of dyslexia. Dyslexia & language processing problems aren't all the same. It is best to have the kid evaluated/tested and many schools won't do that till kids are a bit older for a good reason. A daughter of a friend, who is an exceptionally gifted young woman didn't really read till the start of 3rd grade, worried her mother because you could tell in other ways she was gifted & bright. But once she started reading she quickly made up for lost time. I believe one of the most important things is to have them LOVE reading & learning.
My DD18 has language processing problems and until she was properly tested in 2nd grade all the efforts to help her were a big guessing game & didn't really work. While it's quite possible your child has a form of dyslexia it's hard to help without you knowing a lot more details. What will help one child might not help yours. I don't know much about stealth dyslexia, but do about language based LD's (learning disabilities) and it's often just one small detail that just eludes our children. My daughter could read the individual words, but had a hard time comprehending what she was reading.
