Take heart KJP. I don't think many of us are prepared for these 2e kids. I certainly wasn't with my eg/pg. And he, too, has flipped the way I learned and what I knew about education too.
Unfortunately, I found that since most teachers and schools were either unprepared or not equipped to deal with the eg/pg part, we were at a double loss with the E part and why we ended up homeschooling this year. It became a least worst situation and at the this point the only way that we could deal with the 2e.
Someone once said to me that I need to create my own map and to start with a blank slate on what do with DS and his education. Though this was quite terrifying and scary advice at the time, she was correct - that I had to disregard what how other kids learn, go to school, and don't have the same issues/struggles that DS has.
It can be very hard to make heads or tails out of things with 2e kids and what they need or how they brain processes information differently than the norm. Some teachers/parents may be knowledgeable about ADHD but then not the gifted part. Or not really understand when you've got multiple things like you have going on with your DS or I've had with my DS.
From what your saying about your DS, it could be a processing situation, test anxiety, or something else like dyslexia you've said. Hard to say. You need more information. Hopefully it can be resolved and the teachers will work with you. But like I said, unfortunately not all teachers, schools, or even gifted schools are created equal in dealing with 2e kids. I really wish they were though.