Sounds like you have him on the right level
and well done mum it sounds like you gave him an honest test too
aiming for the exact right level is very difficult if you don't have a set of leveled readers so close is good enough! I think you just need to give him some time with these new games for sight words and you will probably find he jumps pretty quickly. I can't give you more specific advise without more info, like a picture or text copy of the book he got yesterday or a video of him reading. Overall I don't think you need any more advise you seem to have it all working
Thumbs up!
If he is reading simple sentences or one sentence per page books then the site word books are useful, ( and any series will be fine, they all do the same thing, some do it in a more interesting story ) if he is beyond that he may not like them and the games will be better....plus they are free!