I'm curious to why you fixed the improvement in the second bonus of Bobbing Barrel Brawl, but not the other things mentioned, hmm.
I also tried the bonus in Kreeping Klasps that I mentioned. I have managed to get into the bonus 10 frames faster using the method I mentioned. Just jump down in the water as late as possible, fall down the water a little and swim up to avoid the fish and enter the bonus.
This is what I made it look like. I did get 8 frames of lag however, some of it can probably be avoided to save even more time.
More stuff:
It's possible to be closer to the exit in the first bonus in Krevice Keepers, by jumping down as far to the right as you can and turn around quickly to grab the coin. 3 frames (Possibly more) faster.
Ok, this improvement is actually quite major... I thought you only took the slow path because it would be easier in the testrun. In Barrel Drop Bounce, when you getting the koin, if you take the steel barrel and jump down to the left instead of going to the right, you'll be able to save over 100 frames. My quick test got me 101 frames faster, but there's more than that to save.
First bonus in Lemguin Lunge, you can roll into the last penguin that jump up from the hole. Saving you 6 frames.
Creepy Caverns. After you get Squitter you jumped into a barrel later on. If you wait a bit on the web before you jump, you can use another web to skip the barrel. Saving you around 30 frames.
I managed to save about 10 frames at the Koin Lightning Look-Out, but I'm unable to keep them because of the lightning being in the way :/. It involved letting the lightning hit the bird with the barrel instead of jumping on it. If the bird turns around before the lightning hits it, the barrel will fall on its right side instead of left.
Good going with the run, good luck with the last world.