Then yeah, the waiting on the vet sucks but is the best plan. He may need an anti-nausea med. Call them if the email hasn’t been answered by a reasonable time (say after 4-6 hours of their posted opening time today.) Emails are less time sensitive than a phone call.
Food can be swapped or supplemented with plain baked or boiled chicken, rice, and puréed pumpkin (NOT pie filling!) if they’ll take it.
This is the best take I’ve seen yet, with the benefit that it’s literally already been done.
It’d be interesting to see what would happen if they tried to mandate this now, but I’m sure it’s already too late.