Mk13, it sounds like your ds has made good progress on social challenges at this preschool - I don't think I'd be quick to give up on it! JMO, but as the mom of 2e kids, I think that as tough as it may be to see that it's not all about encouraging strengths when our children are really young, you'll be so glad in a few years that you invested the time and effort on focusing on the challenges early on.
Re the allergies - my oldest dd (11 years old) has extreme food allergies. They are getting better now as she's getting older, but she has a history of anaphylactic allergies to a number of foods. Preschool and early elementary school were TOUGH TOUGH TOUGH re managing allergies, constantly advocating/educating, and encountering numerous caregivers/teachers/other parents who were clueless, didn't remember, didn't care, and sometimes, quite honestly simply didn'believe that our dd (and other kids at her schools) actually were allergic or could possibly die from exposure. I am not convinced that you'll get better protection/etc in one location vs another (public vs private school). While public schools come with IHPs and 504s etc, you are still dependent on school staff to buy into the need to follow the plans. Now that I've probably thoroughly discouraged you from stepping outside your house..... here's the good news - we got through it, we didn't *not* send our dd to any program due to her allergies. What we did: we continued to advocate, of course. But we also chose to make a rule that she only ate food we supplied for her. That rule served her very well in many respects - it lessened our worries over her eating something by mistake (because even the best intentioned caretaker might miss something one time), it meant she didn't miss out on participating in anything because she couldn't eat (because we always sent in similar type foods, treats for celebrations etc), and it meant that as she grew a little bit older she began to really own the responsibility for helping to keep herself safe. It also relieved some of the pressure off of her school staff which in turn (just my impression... I could be wrong!).. seemed to help them be more willing to work with me on things that we couldn't control but needed help with - being sure she was safe from crumbs from other children etc (she had a lot of contact allergies at that point in time too, as well as some airborne).
I have to admit though, having him ride on the school bus without an epipen would bother me a lot! Won't they allow him to have an epi on board? Is the bus driver trained to administer one? I am fairly certain that's a common issue on 504 and IHP plans in schools from what I've read online. We haven't dealt with it ever because my dd's never gone to a school that used a school bus.
And one last random thought on the math - I think you'll find that wishing teachers could challenge your child more in his area of strengths is something you'll run into as the mom of a 2e child (or any child for that matter... even with students who aren't gifted). Math is such an easy-to-quantify subject when you're looking at academics... it's easy to think that moving forward from simple addition on your fingers to multi-digit multiplication etc is the thing to do and the earlier a child masters it the better and if they aren't given opportunities for that math-fact-mastery type of work they are going to fall behind where they would have been - but I wouldn't sweat that type of math at a young age - at all. It's great when kids can compute early, but not having the opportunity to practice and advance at those skills isn't going to hold them back from accelerating in math later on. I suspect it's likely tough for the teachers in the preschool situation you're in to add in challenging work, and chances are you're not the only parent who's asked for it. If it doesn't happen right now and you're keen on keeping his math interest up, I'd give him math enrichment activities at home and not sweat what's happening at preschool re the math.
Best wishes,
polarbear