Not a spreadsheet expert by any means, but it looks to me like you are on the right track now. I think the Lantus was probably increased a bit fast (esp. given where you were on the N), my guess is that his numbers were elevated a bit due to the UTI for a while, and then of course it always takes time for the Lantus depot to settle in, so it looked like he needed increases. You even increased from 1.75 to 2.0 despite him earning a decrease (under SLGS) on 2/12, bringing him even higher in dose. It's clear that the 2.0U was too much, so it's good you are stepping down from that. He's even technically already earned another decrease from 1.5U on the 25th (but I agree with the decision not to take it, given that you'd just stepped down from 2-1.75-1.5 in the previous couple days-- could've just been the depot talking).
I would just stick with the SLGS approach for now-- keep getting those mid-cycle numbers, and decrease (or increase, if that happens) by 0.25U depending on what those numbers tell you. Gouda was pretty well regulated on N, which isn't easy to do, so I'm guessing that once you find the right dose of Lantus, he'll be well-regulated on that, too.
Beautiful kitty, by the way!