What you can do TODAY:
a) summarize, in writing, EVERY thing that has transpired that you have direct knowledge of. Send that to all parties quoted in that document, and ask for any "corrections or additions, if I have misunderstood anything." That's called a Letter of Understanding, and it's a VERY useful tool for dealing with educational persons of the weaseling and shapshifting persuasion. {ahem}
b) Pleasantly call/go into the district office and insist that you be given a copy of PROCEDURAL SAFEGUARDS. Now. NO, really-- you'll wait.
c) call OCR for technical advice. Explain that your school is refusing you due process.
d) call 504 director back and recommend that S/HE also "call OCR for technical advice. I'm concerned that the district may be inadvertently running afoul of the law. I know that none of us want that."
They are yanking your chain.
"Other children" unless those children are also entitled to FAPE in a LRE (by virtue of being eligible for IEP/504) is a completely irrelevant issue here.
Other children are NOT "entitled" to much of anything here relative to your son's right to a safe and inclusive educational setting. So yeah-- birthday cupcakes versus your child's need to have a safe classroom? Legally, this is laughable.
That's why they are trying to keep everything off the record. They are trying to keep your son from qualifying under section 504-- without leaving any record that you ever wanted evaluation.