I'll take it. Here goes:

I called an airstrike, like the readio suggested, and killed the huge monster, but now I have no idea where to proceed. All doors are locked. HELP!

I know this is slightly vague, but go ahead and ask questions for hints.

Can you describe the protagonist? And perhaps say something about genre?

Is it post-apocalyptic (or at least locally so - like STALKER)?

No

It's an FPS.

Protagonist appears (though being an FPS we don't see him in game) to be mid-30 male. Well educated. Seems to be able to handle guns well, though he's more of a scientist type of person.

Pass... I very rarely play FPS games ;)

Half-Life?

Yes.

I was hoping no one asks to describe the protagonist. I tried to hide the fact he's a physicist. It practically gives it away.

sooo...
I'm having problems getting past this damn goat in Ireland...

Broken Sword :D

Yep! Your go if you actually want one this time! :D

Yup, this time I want ;)

They've used me! First they put me in a prison. Then they released me and asked me to join their cause. And I did, I defeated our enemy. Did they show any gratitude? No! They said I once again corrupted myself and banished me. Enough with this! This time I'll have my revenge!

Sound a lot like Illidan. Warcraft 3?

Fits well, except that Warcraft 3 is an RTS.

Sure, your turn :) I was about to write something about blindness but realized it was already easy enough ;)
I play other games too, not only p&c ;)

I've started to have this weird nightmares every night, apparently I'm not the only one. Some of the people suffering them appear dead every day.