UV lights don't work. The volume of air passing through is too great. I suggest adding a GPS system to the unit, Global Plasma Solutions. We've done this to three of our homes HVAC systems. It takes care of any musty, moldy odors and mold in your house. Also, check the humidity in your house. You may need a dehumidifier. If humidity is too high, mold can grow. It should be below 40%. Here is another theory that needs to be eliminated. If the smell is a dirty sock smell, it can be an oil leak burning off. Is there any component of the system that uses oil or hydraulic fluid? Both smell like dirty socks and the fumes are quite dangerous to your health.

Put the paint chips - not actual paint - up to the grey striped tile. That will tell you which one matches the best. Or at a minimum take a photo that shows the above paint strikes with the grey wall all in the same shot. And yes dark grey walls can 100% work in your bathroom if the lighting is sufficient. You have half the room in mirror/vanity or light tile so it can use the dark color successfully if the lighting levels are up to par. That means recessed cans and/or vanity light in addition to the LED mirror light.

Fireclay Tile, my favorite, is about 5/16” thick, so approximately the thickness of your gap if I’m seeing this correctly. You can build out a mortar bed a bit, but there are limits. I wish I knew what to tell you. I think the bs tile will probably fill your gap, but then the gap at the joint of counter to tile is caulked.

@Mel Damron - so based upon your comment, I’m a difficult customer just because I wanted my shower pan to be built in accordance with the terms of the contract (which required that the work complied with applicable codes???!!??) I actually made this post in order to confirm whether the work had been done correctly or not BEFORE I discussed anything with the subcontractor. Not sure why a customer is labeled as difficult just because I wanted my shower pan to be installed correctly so it would pass an upcoming inspection (and drain correctly when used). Funny - considering that pros on Houzz + pros on John Bridge Tile Forum all told me that I needed to stop the work immediately because the subcontractor failed to install a pre slope before installing the pvc liner. Also, when my GC returned from out of town, he completely agreed that the sub contractor had failed to install the shower pan correctly. FYI - I am on great terms with my GC - and have engaged him for upcoming renovations for my kitchen, laundry room, powder room, wine room, staircase, plus adding a covered deck + new patio + firepit in my back yard. I also just gave him a car last weekend for his son. My mom passed away unexpectedly, and my sisters decided that I could do whatever I wanted with her car since I had given it to her for a birthday gift a few years earlier. My two daughters both have cars, and none of my nieces/nephews needed a car. I knew that my GC was looking fir a car for his son - and since he has taken care of me - and does great work - I asked him if he wanted it. It’s not a big deal - but between that and all of the new work he’s doing for me, it doesn’t seem like he would refer to me as a “difficult“ customer. Not sure why you felt the need to insult me.