Congrats Sarah,
Cooper will benifit from starting school and it will help you out as well with a new bubba on the way.

I dont know if this will help but -
The theory I try to take with my daughter (physical, intellectual disability as well as autistic tendencies and sensory integration disorder) is to provide every opportunity possible.

I noticed toileting is an problem.
My daughter was in nappies full time until she was 15yrs old. Now she is night time only (just turned 16). I started with toilet timing - sit on the toilet every two hours for 5-10 minutes, dont worry if you dont get results straight away. Be consistent and persistent! once he gets the idea (and when you are confident enough) take him out of nappies for a couple of days and see what happens.
I tried every school holidays for about 12 months and then something clicked. Now my daughter cries if she has an accident. She has limited to no communication but we toilet every two hours without fail, usually she will do a wee but sometimes she holds on until the next toilet time. We still get the occaisonal accident but she has been mostly dry for 12 months.

I was always told "She will be in nappies for ever" but with persistence and consistency (and the financial push) we have done it. I wish we started earlier.

It sounds like you have a very special brave boy. Good luck with everything.

Sjl