Nice job on the floor, Brian. I am a flooring installer myself, i wish I would have seen this post earlier.
What I do,(27 years practice)is I float the floor with the Mapei floor leveler with the additive(watered down white glue)and then just scrape the high spots with a 14" trowel. Keep doing this until the floor is like glass,it may take two or three coats but it dries fairly fast.
You can also accelerate the drying time by putting a fan in the doorway,facing up to the ceiling for air movement.Don't put the fan directly on the floor because the leveler will dry too fast and crack.
I would never use a belt sander because you will get a wavy floor.