EDIT: cl_hud_minmode 1 is the culprit; hud_minmode causes the vpk's to incorrectly load (or not load at all) on anything higher than sv_pure 0. if you load your hud normally and then apply hud_minmode, the vpk's will still work until you restart the game. this seems to be the easiest statement i can make, but i'm interested as to why keeping dxlevel in my launch options while hud_minmode is enabled allows the vpks to work.
just confirmed that it clearly is a config issue. backing up my config folder, creating a new one by launching the game fresh again, specifying the dxlevel, and then removing the dxlevel from the launch options still allows the vpks (mainly, particle_removal) to work in sv_pure 1 (haven't tried higher yet). i just need to figure out what convar (or combination of convars) is causing the vpks to improperly load past sv_pure 0.