Are you using a method, a manual, an online program or are you just trying to get him to read some words?
You need a progression ladder and if phonics doesn't work, you should consider the syllabic method. For example, mat, cat, bat, hat and so on.
I would also pause the audiobooks, and you have to read the book to him and with your finger you follow the text. Sometimes, when reading and getting to a word he should know, you pause and let him complete the sentence.
You can work together on making labels, even with the Post It notes, and you or ideally him write down objects around the house such as fridge, book, chair, door, handle, window, sofa, cup, ... and you put letter in a small bag, and he has to bring you the labels starting or ending with that letter. However letter games are a complement to teaching and learning not a substitution.
For the writing, practise tracing with maze books and tracing books.
You need to have a routine, that includes plenty of breaks. Try to reduce screen time to increase attention and interest.
If he has a formal diagnosis, do you qualify to OT or a speech pathologist ? They should be able to help with literacy .