As far as optimization goes, I've actually been doing that for weeks. I recently ran a cleanup in XWE. More than that, I brought down the filesize from 76 MB to 73 MB through all kinds of sector merging and vertex deletion. Unfortunately, that's pretty insignificant compared to the 30+ MB that'll be tacked on by the music. Just adding all the music that has been made so far has brought the WAD up to 83 MB (though some of it was in MP3 format, so it can be compressed a lot more).
No one can say that the problem with Tortured Planet is waste. I've diligently purged any useless fat from the thing, to the point where there is actually far less waste in Tortured Planet than in vanilla SRB2. The simple fact of the matter is that this is a huge pack full of huge levels. It isn't like Mystic Realm, where the true content is less than 25 MB; even without music, its size is colossal.
Tortured Planet has 73 maps (v9.0 has a new one), and many of the Single Player levels boast several minutes of gameplay even if you breeze through them quickly. In addition to all that, there are oodles and oodles of custom textures, flats, sprites, and other graphics resources jammed in there. I don't know if this is unprecedented in the history of addons, but I'm pretty sure that even with 34 OGGs (the 32 Charybdizs is making plus Midnight Freeze and Fire Flight), music will only account for about one third of the filesize. Therefore, I really think that in the grand scheme of things, the benefit of splitting the file doesn't outweigh the inconveniences. It means the difference between downloading one huge file and downloading two huge files. I think I'll opt for the former.