I have a similar question five years later: Is the 4" matching back splash now out of style? And how long will it stay out of style? Doubt that it would be possible to get a full matching back splash 14 years after the home was built. I am considering removing the 4" back splash and going with a complementary tile or, perhaps, a colorful wallpaper. Thoughts as to how long the short back spash will stay out of style? (I'm old enough to remember bell bottoms - the first time they were in style.)

Here is a link to google, how that backsplash should have been installed. There are some u tube videos too. I watched one video, where they used grout, between the countertop and the backsplash, and grout should not be used there. Caulking shud be done between backsplash and countertop. My backsplash is also caulked in all the corners, rather than grouted. Once you watch these videos and read these articles, you will see that your thinset was put on improperly, and thats why your tiles are falling off. Please read carefully. https://www.google.com/search?source=hp&ei=uI4VW7HdLszKjwTtrqSoAw&q=how+to+install+glass+subway+tile+backsplash&oq=How+to+install+glass+subway+tile+&gs_l=psy-ab.1.0.0l3j0i22i30k1l3.3755.12143.0.14244.41.29.3.9.9.0.173.3348.9j20.29.0....0...1c.1.64.psy-ab..0.41.3556...0i131k1j33i22i29i30k1.0.70wb9L5GlO8

What about just having the Calcutta as the backsplash? Just run it to the bottom of the hood. No other stone or anything else needed.

That IS a little awkward. I'd look for very small molding trim pieces, paintable to match cabinets and sill, to go on that edge from the sill around the corner into the cabinet. Something like a L in profile that could cover the edges. If you have the chance to get it redone, have it end a few inches away from the window (like as far as the stool comes out to the side) and use a Schluter type of edging. At least caulk the edges with paintable caulk and ignore it. The big picture looks good! It'll only bother you when you're at the sink. :)