Oh Star :(
Well, you know that these things are formulaic, right?
My advice would be to really strip it all down. Take the emotions right out, and decide what you can truly say is 'essential' for your DS's educational needs, what is 'desirable' and what is 'ideal'.
When you have done that, accept that a tribunal is not going to go for 'ideal' measures, but that you can push the desirable into the essential with some clever wording.
I know in the past, it has been said to 'shoot for the moon'. In a lot of ways, you need more than anything to show yourself to be a conscientious parent, who simply wants an adequate education for her son.
Try to avoid complicated sentences. Keep everything clear, plain English. Win the tribunal over. Don't try and win the War this time, just see it as one battle.
And ofc, I would help in anyway I can if you genuinely need it for the letter. But, you are very able.