I was wrong about the 8mm socket not fitting. I tried again today, with my new set of allen wrenches and the 9mm. 9mm was too big. I put the 8mm in the plug, and it was a perfect fit. I must have been turning the socket at a weird angle last weekend.
8mm allen fits the 5EAT ATF drain plug. My T70 torx bit is on order for the differential drain plugs.