[2021] MOVED: If I make a computer host a server for me and my 2 friends to play will it help with FPS?

I'm no expert on Windows hardware, but speaking generally yes, it will be less taxing to set up a dedicated server rather than trying to effectively run a server and client on the same machine. Without knowing the specs on your extra computer, I'd say it's worth trying.

Incidentally, there's a harder limit on total zombies at once, which I believe will override your 64 per person setting.