I think he did. If I recall correctly, the reactor almost seems to fall on top of him.
What I find intriguing is that he says "You need me", just as the whole thing explodes, I wonder what he meant with that. Is he talking that he is important with the Combine or for humanity? Or something else entirely?
I think it's more an incredible blow against the Combine. At least for the human sympathisers. For the aliens who took over earth, I think that it's more of a "Death Star" blow. Definately costly, shows that they shouldn't underestimate the humans, but far from defeated.
No idea. Rather interested in what all those other alien things were there as well. It really seemed as if they were massing for an invasion there.
I'd hope so.
Who doesn't? When you start the attack on the citadel, the little scene with him just rocked. First time, I couldn't exactly pay attention to what he was doing as I was battling the Combine soldiers. First I saw him attacking some folks, then he was run over. I fired at the soldiers, until the tank drives by with him in tow. I continue firing, and when I spare a glance to see what happened with Dog, he was about to throw the damn vehicle straight at the soldiers. That was just bloody ace.
His return as well. When I saw a few cars fly by, I thought that there'd be another Strider battle, and was prepping myself... until suddenly Dog came running around.
I hope so. Still, the way I see it, only way that he could have come out of the citadel that is just collapsing is either by sheer luck(that heroes always have), divine intervention, or a certain blue-suited bloke who helps him out.
Doctor Mossman? Definately for the good guys. She's pretty much Lando, I think. Works for the bad guys, until they go too far, and then she helps out to aid the heroes again. I read a theory somewhere where they thought that it was all preplanned by Eli and Mossman, which is an interesting thought. Does any of the dialogue between Eli or Mossman point to this?
Save and sound where Alyx left them, I think... even though Lamar managed to flee again, and was last seen after the credit sequence. (which was ratherquote)
Only way that she could've survived is the same as with Eli and Mossman. Sheer heroic luck, divinite intervention, G-Man.
They're still all over the place, I suppose.
I'd like to think so. His exit was just excellent. Laughing like a madman, running into the fire while unloading his shotgun at the zombies. His laughter haunted me as I exited the level. Still, I hope that we don't get to see him again in HL3, just keep him as an enigma.
With the Combine possibly out of City 17, things might've quieted down.
I really have no idea what you're talking about here.

The answer is maybe.