Biggest things that helped my sob was sorting out his ehcp properly. This lead to independent speech therapy and occupational therapy as the nhs couldn't provide the level of support specified in the plan.
We also introduced an aac device at a young age however you're never tok old. He was non verbal but still continued to use it as he developed speech. It isn't there to replace speech if a person can use verbal language but it takes the pressure off especially if it's something like lamp words for life as the buttons never move places so muscle memory takes over.
We had an amazing mainstream primary that went above and beyond for him, we're still in touch with his old 1:1.
Colourful semantics helped with sentence structure and understanding of the different parts of sentences.
We use lots of pictures/ visuals to support everything.
We use basic makaton signs so he has an extra visual prompt of what is being said. So verbal language, signs and visuals/ symbols all together.
Any written work was broken down into coloured text to match colourful semantics.
Lego therapy but the type by Brick by Brick. Many teachers, ya's therapists etc "do" Lego therapy but if not done correctly and by someone properly trained it's not going to help that much or as much as when it's done properly.
Work together with school so that whatever gets implemented at home gets implemented at school and vice versa. Consistency really helps.
We follow his interests and he does and has always gone out to places, in the community, theme parks, anywhere and everywhere. So he feels part of his community and is used to these places and so we don't stop taking him even when it's difficult or other people find it awkward.
Look after yourself too.