RTF is a global modification that replaces all towns in the game.

Wow, it turns out to be a stupid paw movement – is it because of the IDL? Is what I did similar to how a Yeti moves its paw upwards? And do other basic creatures have this?

I can't say about other creatures, but it's likely that they do. For example, a Cyclops moves its head from left to right, which means there should be a stupid head movement, but I don't know, I haven't paid attention.

P.S. The slipping effect is VERY jarring – it definitely needs to be removed, otherwise it's just a shoddy job.

So, for example, a unit puts its paw down, and that paw slides forward? Is that what you mean by slipping?
I don't know how to fix this other than by re-exporting the animations.

P.S. To make it move 4 squares, you need to slightly increase the size of the creature, i.e., re-export it?

Well, only the animations.