I am glad you have increased the dose. It appears, to me, that Diablo has a late onset- "normally."
I can tell you from my experience with Kitty, that low 200 preshots were hard to get good cycles on. I got much better cycles and numbers on high 200 or low 300 preshots--- I almost hated to shoot a low 200 at any dose, because the numbers were never good.
Hang in there.....you have never had any scary low numbers, even on the "good" cycles, so just slowly increase if needed and work your way to a good dose. You are doing this "the right way!" If there is such a thing. You decreased on an unshootable preshot, found that the reduced dose is most likely not enough and are slowly working your way back up-- PERFECT! AND, last but not least, you are keeping great data in your Spreadsheet and checking for Ketones!
Good Luck!