Hi there, my son has ADHD and the referral to CAMHS at age 10 took 5 years to come to fruition. He started medication 6 months ago at age 16, so just in time for his GCSE's and this has really helped him focus no end.
To answer your question, does it get better - yes!
I think ages 6-10 were the trickiest as they really struggle to self regulate.
My son would have meltdowns after school too and every small change in activity was a struggle. He couldn't go from one activity to another without a big debate and being really obstinate. Just getting him ready for football training took me 30 minutes of prep and persuasion. Fine once he got there.
The best thing that helped him (and me) was routine, routine, routine. Consistent calm routine so he knew what was happening from the moment he woke up until bedtime. I kept it simple and tried to keep it the same day in day out.
Also swimming - that really exhausted him.
He hated too much talking and discussion - too much 'noise' in his head. So our house is quiet and calm. After school he still needs at least an hour of silence to decompress - no questions or discussions about what went on at school - just a brief: how are you, hug, snacks.
If he could have quiet breaks at school that could help. Sometimes I think my son melted down at school due to the constant 'noise' and the time out actually was what he was craving. If school can give this 'time out' before the pressure builds, the melt downs may be avoided - both at school and at home.
I think there is a misconception that people with ADHD will be fine if they are kept very busy and active all the time - this is untrue. Burnout happens very fast with ADHD so time to switch off completely regularly throughout the day (especially from people) is very beneficial. Social burnout comes on really fast - an hour surrounded by people can be enough.
Hang in there and it does sound like you are doing brilliantly - it's just a very difficult phase.
My son is a lovely, calm, thoughtful and productive boy now and this has been the case throughout his teen years. Like you, I was dreading them but it turns out age 7-9 was the trickiest!
Keep going