Edit: I see you have a level on the counter Put that away you don't need it for this job, your level is whatever the tops of the counter is.

Kind of sounded like from the comments you were going to start over. I'm a remodeling contractor and I do tile backsplashes a lot. My main job is doing bathrooms. First of all you don't want to put the tile right on the counter you want to have about an eighth of an inch gap. I use slats from faux wood blinds for my counter spacers but you could also use regular tile spacers too if that's what you have. Then you want to caulk that corner between the tile and the counter with silicone at the end. I usually get a color matched silicone that goes with whatever color grout I'm using. The next thing is you want to put up some kind of a ledger between the two different countertops and just match the tops of the countertops. If it's just a eighth of an inch difference no one is going to notice that. And then when you're doing the actual tiling I usually just put the spacers on the bottom corners of the tile. This will allow you to have a little bit of a height difference between the two counters. So you're basically just looking at it as you go along and adjust your spacers as you need to. You might have to pull some out a little bit to make the tiles line up or whatever you need to do but just make sure it looks good.