Any UPS worth the money you payed for it will act as a perfectly fine surge protector. I don't really see a need for your computer to be behind both.
As for surges from Ethernet, as long as all of your switches are protected you should be fine.
Q1: Rare (Unless you happen to have BIG bundles of copper burried underground)
Q2: Throw away the surge protectors and get a real UPS if needed.
Q3: You could have the ethernet connection go through a switch... that way the switch gets toasted not the server.
Q4: If you still want to use your power strips do Server --- SP --- UPS --- Wall
with ethernet: Server ---- SP ---- Wall.