I have a similar layout and didn't tile the side wall. IMO it's personal preference.

You could tile up to the bottom of the cabinets. Or not. I have wall paper on my two side walls and it is not a problem.

No. They symmetry of that run gives it a furniture hutch feel. the sidewall is not part of the "furniture" piece.

You don't have to tile the side wall if you don't want or you can if you like the look!

If you choose no backsplash there, make sure your counter installer knows this, so that they get a tight fit between the counter and the wall.

"Don’t do it - IT'S AWKWARD. It just kind of hangs up there in mid-air without a proper place to stop."

https://carlaaston.com/designed/side-backsplash-dilemma

Oh gosh no. Stop the backsplash at the corner on the right (flush with the end of the upper cabinet) AND MAKE SURE HE STARTS THE TILE flush with the upper on the left - not all the way at the edge of the drywall. If there is no bullnose tile or trim, make sure he uses a Schluter edge. If he doesn’t know what a Schluter edge is, get another installer.

I’m thinking no. I think it just makes it look unfinished. Thank you all for the tips!

No. It will look odd...

Noooo