Most likely wont put that in considering they haven't responded

try this in video setings:(change from the disconected game menu, or else it will take more time pro procces) textures: low, shader: low, color correction: disabled, filtering: 2x, multicore rendering enabled (then close the game and launch again, or else some textures will apear as missing textures) also another trick is to have other npcs to help you kill the horde of enemies, so they dont gather too much. and also again, check the setting in vj base, like disabling blood pools or set fade corpses and gibs to the minimun.
the other options does not affect much. but you can disable antialiasing or put to the minimun, and wait for vertical sync, (but the game will not look much good when you move with that disabled)
sometimes gmod won't suggest proper video settings for your card, nonetheless the game will work fine with minimun stuff. but if you want to have more stuff on screen and dont have a proper card, you need to reduce what usually makes the graphics more system expensive, like textures, most new addons have hd textures, with does not fit older video cards or on board cards.

also most important set prossesing time to 3 in vj npc options