Hey, one thing to note (in case you either didn't know this already or forgot to add it) is that Jumpman being on the same x-axis as a ladder steers barrels as well. So, even if he is several levels below a ladder, if he is directly under it, it steers barrels as though he is sitting on it. It's hard to tell from the gifs if you've incorporated this element already, so I thought I'd mention it.
Also, I don't remember the details, but there is something special with the first barrel (or maybe it was a timer based thing that can affect all barrels until a certain amount of time) where the first barrel will always take the first ladders on each levels that it reaches. You'll have to ask around or look in some DK code threads to find out the precise way this works (maybe it is easy to find in the code).