Do you have suggestions about approaching the teacher again? I get the feeling the school thought my issues were with THEM. Really, my goal is to help my ds not only tolerate school, but find value in it.

Yes, they probably do think you're *that* mom, but you know, you just might have to get comfortable with that! ;)I would politely follow up in a week or so (after the original meeting) with an email to the psychologist asking what assessement would be given, and when, as far as math. DO NOT be afraid to really ask questions, especially in light of your ds's anxiety on timed tests. Let them know if you think the proposed test would be a bad fit. Make sure your ds has some idea what to expect.
I'll be honest, I rarely followed the advice to "ask for help" or "talk about his weaknesses" when it came to my one ds. The other kids, yes, but with ds12, they seemed to already see too many weaknesses due to his poor speech and OT skills. Anything I said that added to that, they seemed to view as reason not to give him more advanced work (2E wasn't well known/accepted). Definitely ask to see the assessments they've done as far as reading. I politely requested copies/viewing of EVERY assessment done by the school, many of which were put in his file but not necessarily shared with me. I would ask to meet with the teacher on a monthly or quarterly basis. Even the teachers who WANTED to differentiate often got busy and it fell by the wayside. Another thing we did (and yes, I know it's only October :)) was to ask in March for a "transition" meeting with the current teacher and the lead teacher for the next grade(in our case, teachers weren't known, so we met with the lead). We were never refused regular or transitional meetings and we found that the consistent regular meetings really made things easier. It wasn't so much "why aren't you doing this?!!" but "So, what enrichment are you considering for ds next quarter?" I would bring examples to each meeting of things he was doing as well.
One hard thing (that I know MANY parents here have found) is that the school can pounce on any missed thing - if they give your ds an end-of-third grade math assessment, he might not know lattice multiplication or the name of the distributive property, but he might be able to do multiplication and division just fine. You really have to be able to talk through the assessments and perhaps prepare your son a bit for bits and pieces like that.
I also think it's imperative to get school and/or district administration involved. The teacher was often afraid to say yes without the principal's buy-in, and the principal hated to make the teacher do extra work, but the district level gifted and/or curriculum head would often blithely agree that "oh yes, of course we differentiate, and sure, we try to individualize for each student." Sometimes I felt bad that they'd agree to big conceptual things without having any idea of the work needed to back that up, but I used that to my advantage a number of times.
There are no easy answers in kindy, because frankly, a lot of teachers still believe that everyone will "level out" around third grade. UGH!!!! In each of my kids' cases, I found the exact OPPOSITE to be true. As they got older, their bits and pieces of knowledge shone through, and as tests got harder, they pulled away. You can only go so far on the state testing (and frankly, some of the questions are so stupid and confusing that my kids would get them wrong even if they actually knew the concepts) but on the EXPLORE or SAT, you could see the wide gap between them and their peers. I had my youngest start the EXPLORE in 3rd grade and it made a huge impression on the school (again, I took it to the district, as well as the teachers, because the Director of Curriculum really understood the magnitude of doing so well on an 8th grade test).
Don't back down. You don't have to be rude, but you can be polite and persistent. I volunteered constantly in the classroom, became active in PTA, remembered the school secretary on every holiday, and tried to be as ingratiatingly sweet as possible, while continuing to request what I thought my kids needed. It gets easier to show their knowledge with every passing year, as they get out of rote computation in math and start actual discussions in reading/science/SS.
Oh, and every time you meet with the teacher, or anyone, follow up with a note IN WRITING. I always, always confirmed, "it was so nice to meet with you, and I'm excited to hear about your plans for my ds. My understanding is that he will (study independently) (do 3 AR tests a month) (have an alternate spelling list) etc....
Good luck!