Yeah, your speech skill is too low. You talk to two different scientists to have the following effects:
Release virus: lots of XP and kills off random techs and citizens (including the president's secretary, so you don't get her funny dialog) Talk to the man on the level with the president.
Destroy the Reactor: talk to the guy ont he reactor level in the room with the guard. He'll shut down the computer and start a ten-minute countdown for the meltdown. This, of course, also nets lots of XP (you can't fart on the Enclave without getting a few 1,000 XP).
You can talk to those two doctors (One is Dr. Curling, I forget the other's name) regardless of weather or not you've been shooting people along the way, so, if you go in guns blazing you can still net the XP from these quests if your speech is up to it. You needn't talk to either of them; releasing the Virus doesn't kill anyone who really need to be dead, and starting the meltdown can be done by disabling the computer controlling the reactor. (Do that with a pack of explosives; plenty of them in the Enclave, hopefully you brought some since there aren't any on the reactor level and you *don't* want to go through the puzzle room again. I learned that the hard way.)