Headshots are in regular FPSC already, no need to use a Mod for that. Attach the headshot script to the enemy's "Appear AI" field and that should let you headshot them.
To answer you questions a little more specifically:
1) Create a HUD containing your text and have it shown at the start of the level (via triggerzone script probably)
2) Been answered, use a soundzone
3) Grab a recording program and talk into the mic.
4) I think he IS wanting a character that doesn't try to kill you... well, basically you give them a script that DOESN'T tell them to kill you.
5) I... don't think you fully understand the concept of how games are made. What you must first understand is that everything shown to the player is an illusion. Things are not always what they appear to be. Zombies staggering from a gunshot? Well, those are most likely animations, they are NOT derived from the impact of the bullet as they are in reality. Animate your zombie to stagger from a gunshot, and have that animation played when the zombie gets shot.
More blood? Go change the blood decal. Or, you can use the AirMod blood, which, I believe, is in the official version now. I don't recall how to activate it, so maybe someone who does will drop in and enlighten us.
I highly recommend that you open up the ofpscguide.pdf file in your FPS Creaotr/Docs folder... read the scripting tutorials in there, and you may be able to come up with solutions to these yourself.
The one and only,
Only those who sow the seeds of their desires will reap their benefits later.
However, I have seeds of my own to tend to. I don't have time to be someone else's watering can.