I think I may have worked out the problem with the wall covering. I'm used to holding the shift key and the wall covering being applied just to all the wall pieces with the same covering as the initial piece of wall you click, but with Sims 4, when you hold shift, it applies the change to the whole room, even if it gets to a section with a different finish. At the time I was having the most trouble with it, I was chopping and changing where the walls would be and kept painting the new parts, so it just applied it to the whole room, including the back wall of the kitchen where I had the tiles.