I meant a Blender add-on which reads and writes Source Filmmaker DMX files, sorry to be vague. Sorry also that I don't have the time or motivation to do this myself.

Looks like the parents of the bones that your model uses are being compiled in.

Please upload a .blend file demonstrating this problem.

Units can be configured in the Scene Properties panel. But the Source tools don't pay any attention to them. You will need to scale your model manually.

That means "no".

This isn't supported because the tools are for creating regular game animations, not Source Filmmaker movies.

These two use cases share the same data format, but their feature sets do not entirely overlap. I've always felt that trying to support both at the same time would be too confusing for users who don't understand the internal details of these formats.

A different add-on for SFM could be created based on the Source Tools.

The image links are broken, but the long and short of it is that VTA sucks for import. Try to get a DMX decompile instead.

This is probably because one or more bones from the animation either aren't present in the model, or are muted in the Blender scene. This means that they don't move, and cause the rest of the animation to look weird.

The changes haven't left my computer yet. Please try to upload your file to another site so that I can test whether I've actually fixed the issue.

I tried that and couldn't reproduce the problem. If you have the time, please can you try to import the model into a new blend file and see if you can get it into a broken state.