Yep. 319 of the 354 MB are .wav files. That could be knocked down to 32MB if it were all oggs (it's SDL, so you get ogg for free). Smaller, if you drop stereo for the sound effects. Everything else appears to be pretty tight.
Still, like you said, this ain't final. I'm sure it's already on the dev's radar.
Yes, it's on my radar.
Being in active development the assets are a bit unorganized and are definitely not optimized. I have quite a bit of sound and art that is included in the game that will wind up not being used I will need to remove in the final version and the audio will all need to be optimized and renamed.
It's not a big priority for me to optimize the content size at the moment, but I can probably cut a good chunk off the install size without too much effort by just removing unused music and optimizing the tracks that are left as well as some of the larger sound effect files. I'll work this into a future patch release.
Probably won't be swapping to .ogg for sound effects, but definitely something I'd investigate for music and longer ambient soundscape tracks.