Hi, really sorry to hear about your situation I don't have any advice aside from possibly paying for private SALT sessions whilst you are not recieveing them via school? Of course if you can as I know they are expensive. Either that or you could ask for exercises to be sent home from the SALT therapist and try to do little bits at home, but again I know this can be tricky! As for waiting times for appointments I'm not sure there is much you can do, the doctor has done the right thing in pushing for it, and I would suggest to keep asking them to do the same over and over to hopefully help, however I have had the same position (before Covid) and we still had nearly a years wait despite it being out through as urgent. 
I really have been where you are, and still am in many ways, my daughter is 7 and has had glue ear since she was 2, we have had 3 lots of grommets, adenoids and tonsils removed and a set of hearing aids. It's hard to be taken seriously with glue ear but please know your not alone xxx

If you can I'd look to see an ENT consultant privately. I knew my daughter needed to see our consultant when they were just opening clinics again and it was very worth the money to get her seen quickly privately.

Also, when my daughter got glue ear we were able to treat it using an ear popper which wasn't available on the NHS anyway.