GMOD Server Lag & Low FPS at 30 players

[PliC1]

Server OS: Windows Server 2008 R2
Processor: AMD Opteron Processor 6386 SE 2.80 Ghz 6vCores
Ram: 8 Gb
Game(s): Garry's Mod Darkrp
Start Up Command: srcds.exe -console -nohltv -game garysmod +r_hunkalloclightmaps 0 +port 27060 +gamemode darkrp +maxplayers 50 +map rp_evocity_v33x +host_workshop_collection 365739939 -authkey ******
Addons : http://steamcommunity.com/sharedfiles/filedetails/?id=365739939 + ULX & Darkrp gamemode

Connection : ~300 Mbps download, ~100 Mbps upload

Screens : http://prntscr.com/66e1k4, http://prntscr.com/66e2qu, http://prntscr.com/66e30s

I have tried to use srcdsfpsboost, open Media Player but it doesnt work.
I have tried -tickrate or commands like sv_maxupdaterate in server.cfg but it doesn't work.

What to do ?

Please, help :'( !

Sorry if i have a bad english... (i'm french).