I did the chair thing after the second attempt. It works, I wait until the big fat guy is outside the second door, open the first, wail on him with the chaingun, and watch him fall, but when I eventually step outside I kept dying instantly by guys I couldn't see. Two or three thwaps would kill me before I could even locate a target with the binoculars.
And, jaded as I may be, FEAR multiplayer is complete garbage, at least in the beta form. Garbage, among the worst I've ever played. BF2 was great fun for a short period of time, FEAR blew from the first instance. I've said it in a few dozen threads already, so I won't repeat, but it mostly has to do with weapons being overpowered, everyone dying before they know they're being shot at, and endless cycles of killing the guy that spawned before you by killing him in the back while he's reloading only to be shot in the back by the guy that spawned after you while reloading, only to have him killed by being shot in the back while he's reloading, etc.