Hi guys, I am currently updating our guest bathroom shower. In an attempt to reduce the scope of work, we are keeping (reglazing) the existing bathtub, but we are tiling all the way to the top of the ceiling. I have removed the old tile and drywall at the back and sides of the shower and I have them down to the studs. The plan is to put cement board as a substrate (Durock) overlain by Schluter Kerdi, overlain by 3x6 Subway tiles. For the edge of the tile, I was planning to put a Schluter profile. Now I am in the phase of putting back the walls together prior to tiling, and I ran into a small issue. The bathtub does not exactly fit the space available. As such, when placing the cement board over the tub, there is a tiny space (about 0.2 inches) behind the cement board. This causes the proposed cement board and the existing drywall to not match, as shown in figure 1 below. I forgot to mention, to make sure the cement board is vertical, I will need to shim to make up for the gap using roofing felt, unless you guys suggest something better. I tried looking into alternatives, but I could not find a piece of wood that would help with this tiny space. In order to close up the space and make up for the difference, I was wondering if you guys knew of a product or profile which could help hide the difference, such as a corner profile. Please see Figure 2 below. Can you guys think of a different/better solution? I haven't been able to find a profile with that shape. There are plenty of T moldings for floor transitions, but I haven't been able to find anything similar for walls. Would you still do Figure 1 and put caulking in the edge? I really appreciate your help and opinions. Thanks!

I removed wallpaper from my walls with fabric softener and water. Do I need to clean the solution off walls before painting and what would be the thing to clean them with?