I would say stick to the basics. Sorry to say this but that server.cfg and plugins you have is a mess. Remove all unwanted Windows services running on the background, Google more ways to stop every bit of it, once you stop all unwanted services, your Windows PC memory load will come close to 500 MB Idle on a 32 bit installation.
Revert back to stock/clean HLDS server package and test the server again with at least 4 players as in the screenshot. If the results are the same, try
ReHLDS and even if that didn't worked, might be hardware related. Just my 2 cents.
Plus if you use this PC to do anything else while the server is hosted, better not run the server because it's not gonna multi-task much with that hardware.