haven't read all posts, so sorry if repeating.
OP; YABU to demand an apology. I really don't see there was any need for your ds to have gone without food or drink. He could have and should have asked for help at the office, from friends, his form teacher etc etc.
I can imagine the teacher being abrupt if he has shouted out in the middle of the lesson. He may not be a disruptive child, but even if it is something important, if a child tells it to the teacher at the wrong, or inconvenient time, it is disruptive. Even if he put up his hand and waited to speak! Imagine the teacher is trying to get across an important point. The class have struggled to grasp it. She's been explaining careful and senses the fog is beginning to clear. She asks an important question to gauge if they have understood. A few kids put up their hand. She chooses your ds. Instead of answering her Q, he says his water has spilled. Queue much hilarity from the class.
I have to remind my kids often that there's a time an d a place for what the want to say. Ds wants a skateboard for his birthday. Asking dad, who is 10 minutes late for work, and can't find his car keys and getting more and more irate, this is not a good time in order to get the response you hope for! Most kids, SN or not really knead to learn when to ask. Sounds like your ds chose a bad time.
I think your reaction, heartbroken, demanding apologies, speaking to more than 1 person about it, all totally OTT.
Surely all that's needed is a word to your ds to be careful with his timing and to see help at the appropriate time form the appropriate source.