If the room is still red it’s possible that lighting didn’t get rebaked and/or the floor/wall objects are really shiny and receiving some of the red color. It’s hard to say without having the project in front of me. It sounds like you’re doing everything correctly.
Lightmap bakingmay take a while. The videos may be a bit deceiving as I cut out or speed up the process as I wouldn’t want to have a 10 min video of lighting being baked. If you really want to speed up lightmap baking set the lightmap resolution to something like 2. That setting tends to determine how quickly you’ll bake out lighting.
