I think it's good you gave that shot, next time I would probably try even less than 0.2u, just a fat 0 maybe (just a drop basically). Although there's nothing wrong with waiting at a 189 to see if he brings the # down on his own, there's nothing wrong with giving the insulin, and it got him back into good #s which is great.
If the antibiotic cream doesn't seem to be working, I would probably head to the vet if you think he has an infection. Although I know in your shoes I wouldn't want to (vet might argue against home testing, though it's clear from the data you've got that the testing has helped you get Squishy in an awesome place BG-wise!!!).
I would probably also give his ears as much rest as you can - with Bix if I had a heavy testing day then I would only test PSs the next day. Although it's great when we all can get lots of data, I think you have enough collected at this point to let some of it rest. If you give a tiny shot, I would probably just skip spot tests, or at most do one at +4 if you are worried about low #s. You know the food is working well for him, so even if you see a lowish #s at this point, I don't think you have to keep retesting a lot. I would if you got something scary like a 20, but if you get a 50 at +4 on a tiny dose and you go ahead and feed, I think you can feel comfortable he will be fine based on past data. If it were me I probably would not test any more today til bedtime - I'd be tempted to even skip the normal +12, since there's a good chance from today's #s it won't be shootable anyhow.
Or take a couple days off seems ok to me, though I'd hate to see you lose progress if his #s do go higher - seems like he is really really close right now and might just need a couple more token doses here & there to go all the way. [anti-jinx!!!]
Remember also that infection can raise their BGs, and pain also if his ears are starting to hurt. And of course infections like that can take some work to get rid of, so if you give his ears a day or two rest altogether, and also keep applying the cream, and his ears don't look a lot better, I'd probably go ahead to the vet...