All I want to do is
1. Start with a WMF file.
2. Chop out some parts. I may keep audio, might not.
3. End up with a non-WMF format (QuickTime preferred) and have the resulting
file size somewhere in the neighborhood of where I started.

The issue is that quite literally every attempt I make (software, filters,
compressors, key frame, frame rates, and so on, even removing the audio
track) increases the size quite a bit. A 500KB movie can jump to 1.5 GB, for
example

It's as though WMV is the most compressed format out there, and converting it
to anything else therefore must increase it.

Is there a key element of this process I am missing?