I agree with Errant. I almost always prefer the tile to die there than carry around the side wall. I've been living with painted backsplash area for almost 3 years and haven't needed a touch up in paint except maybe where the raging flame from my CC rangetop has discolored the are directly behind the center rear burner from my extremely high heat searing and stir frying.

As a Certified Red Seal Tile Setter the substrates (sub structure) and prep work are crucial elements and have a direct affect on not only the finished product but also the long term performance. Since this project involves a kitchen back-splash, there is no need to buy/install cement board of any type or a thing of the past called Green board. Like any tile job, everything must be level/square and solid first! Removing existing tiles and minimizing the damage to the existing wall board requires the right tools and a certain degree of patience. Personally, I have never seen cement board behind any type/kind of back-splash tile(s). Ceramic tiles are the most porous kind of tile and should be properly sealed as well as all grout lines. Also, in water areas, your grout line thickness should never exceed 1/8 of an inch. This helps in minimizing water penetration and also helps in the visual appeal. The idea is to showcase the tile not the grout lines! Secondly, and equally important is to try and get the grout color as close to the main color in the tile, that way it gives a visual appearance in being one large piece of tile, although it isn't! Solid color tiles should always be complimented with a slightly off color grout (i.e. white tile - off white grout). Your investment is in the tile, not the grout line, so it makes sense to showcase the tile! For DIY people, forget spending your time looking at 50 different videos on YouTubes or even worse, the advise you get from some hourly clerk at your local improvement store! It is to your advantage to buy your tiles at a place that specializes in tiles only and nothing else! They will and should supply you with everything you will need material wise to do your intended project. On another note, buy a few tiles first; take them home and place them where they are going to be installed ( tape them to the wall if that is where they are being installed); stand back an look at it to see if you like the color/size and the pattern. What any tile looks like in a showroom can look a lot different under different lighting conditions!

Your first photo shows an outlet, not a switch. If it can't be moved to the left, leave it where it is and hold the backsplash back a couple inches from the cover plate. The fact that the backsplash doesn't go all the way to the end of the counter won't matter.

Why doesn't he want you to move the light switch? It's soooooo easy! Do it when he's not home and see if he even notices. Schluter is no good when it shows up in a classic kitchen like yours (although it has its place)--definitely find a tile with proper trim pieces--and corner pieces--surely you wanna wrap that corner! And, not to side with DH, but if you DO wrap the corner, it might be better to tile higher than the sill because it might look weird on the non-window side to have a stubby backsplash. I can't see that side so I don't know. I've used Fireclay and Pratt&Larson because they make all the trim pieces you can imagine. There are others of course. The need for trim pieces will limit you, but it's worth it.