@neobrain thanks for the advice! this software is extremely new to me so i didn't want to risk (time) pressing buttons i don't understand. disabling TSO memory and enabling reduced x87 precision yielded some hefty performance boosts! at 640x480p, half-life runs very competently averaging 30-50fps. very impressive for the pi 4b's little broadcom chip!
try as i might, library forwarding has not been without issues. steamwebhelper fails to launch successfully with asound, drm, or waylandclient enabled, and forwarding GL results in ELFCLASS32 and GLIBC version errors. if you think this is worth a github issue, i'd be happy to report this! forwarding vulkan has been pretty harmless, albeit very inconsequential for my test case.