First things first: update to AT LEAST v117. I'd recommend going all the way to 119 to get access to the latest features and stuff.
Secondly, what script are you using to get the zombies to spawn? And have you set the min/max spawn numbers for the zombies?
Third, I think you did the right thing by going through his game and setting the dynamic stuff to static so it's part of the level geometry and not separate like dynamic entities would be. That's a great start to speeding up the game he created. Another thing to check is the lighting in the level - static lights, dynamic lights, switches, and entities for lights can all affect speed.
Again, let us know what script you are using, and what you are trying to do in the script that doesn't seem to be working.
Priest of the Church of Joe Wood
In memory of Nanee. 9/1/1993 - 5/16/2009. Rest in Peace, little girl.
