use the command "mat_dxlevel 80" or put -dxlevel 80 on your game launch settings (if using source unpack, right click the portal.bat > edit then put it there) and after you launch the game once, remove it from the launch settings (also if you can't help, don't answer? lol)
if you used vault save, or loaded quicksaves during the run = RTA if you did not use vault save or quicksaves = SS
yes they work a lot better in 60fps
you can bind jump to a mouse button, but as Evandar said mouse wheel is better
if you use sar + livesplit it should work normally and accurately; remember to use the commands sar_speedrun_smartsplit 0 sar_speedrun_offset 0 sar_speedrun_category Coop
and ofc enable the autosplitter in Edit Splits
don't put them on the video link, put them on the description. it's hard enough as it is to find runs with actual videos
use sar and srconfigs, makes it easy to record demos and a LOT of other stuff