How do we spread server load across several dedicated servers? Also is it possible I use one server for mysql and one server for everything else?
use a hardware load balancer, it works great for me. I have 2 servers and then a mysql database server.
Some cheaper alternatives; http://www.linux-ha.org/ http://en.wikipedia.org/wiki/Round_robin_DNS - easy to setup, but not very balanced. Seeing as you've already mentioned moving MySQL to another server you're probably not interested in either, yet.
Bare in mind that if moving MySQL to another server you should ALWAYS keep them on the same network - otherwise latency would kill your sites.