My concern is that he himself gets frustrated over his inability to figure out words on his own, he asks and he recalls the word always after that. BUT with words that start the same and end differently he always always struggles. So the, then, them, that, those etc - he always reads "the".
I think that he has taught himself the shape of the words he is reading and remembers that - more like an image than a word made of letters.
This sounds similar to my son, although he does have some phonics ability (he's 8). He has a language processing disorder, and for awhile I thought he had dyslexia.
He can read 2-4 grades above grade level, but I need to be there to catch the words he doesn't know. The more basic the words are the harder time he has remembering them because he confuses them with each other (the longer, more complicated words have more elements that he can "grab hold of"). When he encounters a new word he'll give it a shot, sometimes get close and sometimes he's not even in the ball park. Once I tell him what the word is he remembers it, and if he encounters another new word that is similar, he'll call it the word that he has learned, rather than trying to sound out the new word.
My answer to this has been to build his vocabulary with exposure to new words by having him read out loud to me. He or I will follow the words with a finger as he reads and when he doesn't know one, I tell him what it is.
I always choose above grade material so that a) he has this new exposure and b) if the text is too easy he gets silly and squirmy (i.e. bored).
Something I did with my daughter might work for you and your son. She was an early reader, very phonetic, no problems at all. My issue was that she was zooming through the books we had, buying new ones was costing too much, and my son was too hyperactive at the time (DD3, DS2) for the library. Anyway, I started writing stories for her.
You could take the stories that your son reads fluently, use that vocabulary that he has memorized and write new stories, but add in a few new words to give him that "new word" exposure without overwhelming him. Try writing stories about him and his life to keep him engaged.
Meanwhile you could ask about getting him tested... the more information you have, the better. Vision testing is an excellent idea. My son has strabismus (wandering eye), and it may have impacted his earlier reading. He's received excellent care, no longer needs his glasses, and has good stereoscopic vision. His doc is really pleased.
Good luck - I hope it all goes well
