The tile guy came back today and laid down the grout throughout the bathroom, and it looks great. All of the strange areas between tiles are gone completely and I don’t see any variation at all, which is a big relief. I think he was happy to get the check and get out of here.
Unfortunately I fucked things up by not specifying the right wire for the underlayment. Because of the way we originally wired the room (for just the floor heat) and the late decision to add a wall-mounted heating fan, we kept one circuit in the panel, and I was supposed to specify 240-volt wire for the floor heat. 120 is more common, so that’s what he put in. We can’t run both systems on one wire, so I’ve got to have the electrician come back out and fish wire through the walls to support the wall heater. Which is not going to be easy or cheap.