Kind of a sloppy mess of a class. To compensate for bad flamethrower DPS they buffed airblast. To compensate for still having terrible DPS they buffed the airblast harder and gave the pyro the degreaser so that the buffed flaregun and already devastating axtinguisher are even better. Nothing OP here, just a bunch of stupid bandaid fixes in the form of crits, crits, airblast abuse, and more crits.
Regardless it's endearing in terms of versatility. Thanks to a handful of unique and effective unlocks, the pyro has more available to him than the basic "Be aggressive, be passive, now be aggressive again" that every class shares. Pyro isn't particularly hard to play DM wise, but it's the ability to know when and how to utilize different weapon combos that separates a good player who's playing pyro from a good pyro.
To answer your questions: No, see above, no.
#03: why are the crits so bad? The only annoying thing about encountering a pyro is the fact that he locks your movement. Even though he's dishing out crits left and right, only axtinguisher crits do significantly more damage than rockets, pipes, meatshots, etc etc, and that's only at melee range. I don't really see what's wrong with "critwhoring" from a gameplay perspective, but from a balance perspective, it's a very lazy approach to patching up a class that hasn't had any direction in terms of balance for about two years.