A) ..f6 is *usually* bad, yes (if you go through some Berlin games, you'll notice that every guideline gets broken now and then - no different from any other chess guideline).
It certainly isn't an easy pawn to win, but it can force White into concessions / paralyze his pieces.
Most basic idea: You play Nf5-e7-g6, and a Rook on the d-file. White play his own Rook on the d-file and plays h3 to stop ..Bg4. Now, how will White ever get to play f2-f4 (which he needs to get any sort of active play going)? He can't move his f3-Knight since it is protecting the pawn, Bf4 obviously doesn't help (as now the Bishop is blocking f4), and getting the other Knight to d3/c4 plus keeping it stable there somehow takes a LOT of time (or may be downright impossible).
B) (Generally) e6, not c6. It blocks the e-pawn (avoiding any nasty e5-e6 surprises), keeps the queenside in check (eg largely stops Nc4), keeps the kingside in check (threatens ..Bg4, halts g4) and threatens to switch to attacking maneuvers after some piece exchanges (..Be6-f5-c2). On top of that, it is largely impossible to challenge at all. Yes, it most certainly IS strong.
If White puts all his pawns on dark squares .. well, b3 becomes a rather beautiful square for your bishop. White isn't getting anything on that d-file for the rest of your game, and ..Rd2 at some point makes white lose his entire queenside.
C) Confused about this entire paragraph.
1) Black usually doesn't have a pawn on g6, but a Knight (not that it would matter, since you can't play Rh6 anyway if White pushes g4-g5).
2) The entire point of h3-g4 was to be able to play f2-f4-f5, as this is necessary to advance the pawn majority. If White plays g4-g5 in response to ..h5, his pawns are on h3-g5-f2-e5.
All of those pawns are weak (After ..h5-h4, the h3 pawn will forever be under fire of the Bishop, the g5 pawn can easily get attacked by Rh5, if piece exchanges happen the Black King can just eat four pawns in a row), f5 will NEVER get played (nothing to cover that square.. not to mention Black can just park his Bishop/Knight on f5 now), and white doesn't have a single threat left (what is that pawn doing on g5?).
D) I am rather confident that if White just gives away the e5-pawn, you should win this almost every time. Likely not against best defence, ie if you fought Stockfish you wouldn't; but Black already has the "easier" time playing his position WITH the wedge on e5. If White just gives away his pawn, you're in an endgame with better pieces, a more centralised king, and just a pawn up (doubled, but still). You can just trade down some pieces and push some pawns and wait and something will happen eventually.
Here, 5 games between players of varying skill levels to show some points:
http://www.chessgames.com/perl/chessgame?gid=1421957 l'Ami vs some 2350.
First of note is of course that a 2650 isn't afraid to enter the Berlin endgame against someone rated 300pts below him. May tell a thing or two.
Game ends in a silly blunder, but ..Bc2 wasn't exactly possible to stop in any case.
http://www.chessgames.com/perl/chessgame?gid=1802837 Rapid between two 2650+
Picking apart the white position with the superior pieces. Note that light square domination throughout the entire game..
http://www.chessgames.com/perl/chessgame?gid=1772851 Nakamura vs Topalov
Pretty model game (aside from 22. ..f6). Topalov being one of the most famous Berlin practicioners btw tells a few things about the opening as well!
http://www.chessgames.com/perl/chessgame?gid=1800907 Kamsky vs 2650
Breaking everything I said and still somehow winning. Magical.
http://www.chessgames.com/perl/chessgame?gid=1787309 Low rated (1700 vs 2200), but still a showcase of how treacherous even the most basic positions are.
Position after move 27 looks about as dead drawn as a position can look. Same pawncount, both with silly doubled pawns, inactive rooks on both sides, opposite coloured bishops.
Then White stops doing things and just waits, probably offers a draw on every turn or something. Black just plays natural moves + uses his superior bishop, and wins effortlessly.
Aside from ruining your fun, is this a bad thing though? [..]
Not saying that it's a position to be hugely excited about, but it seems that Black is more comfortable in the short-term.
Oh no, it certainly is a comfortable position, and might even be easier to play for a win than the Berlin proper - but it's always a bit sad when you learn X and then no opponent ever plays X.
The French Exchange is not a "weapon" anyone would be afraid of -it just gives Black an easy game from move 3-, but it's still annoying to learn all that Winawer shit and get ed5: on the board in 80% of your games; 5.Re1 is similar business (and this stuff is a big part of the reason I am shying away from the Marshall)
This would be great if we can manage to work around timezones somehow.
Might be easier to connect if you add me on Steam (isavulpes) and we just see when we're both online. Sick username, btw o/
E: And as said, regardless of your opinion of the Endgame, I would be very surprised if you didn't majorly get 4.d3 or 5.Re1 on the board;
The former being an easier normal Ruy (spent a tempo on d2-d3 instead of getting d2-d4 in one go), the latter is similar to the Exchange variation except White doesn't have a way to get a passer on the kingside.
So, even if you think the Endgame proper is a draw, at your level no less (which I would heavily disagree on) - when you won't enter it much, how much does it matter?
E2: To extend on the drawing question -
How likely do you think are you going to win from the starting position, as Black, against a White player who is no worse than you as a player, but 99% content with a draw?
He'll play some d4-c4-e3 or even d4-c3-e3, put his pieces on decent squares, block your active play with stuff like a4, and just wait.
Generally, there won't be much for you to do without taking some risks. Which then very well may backfire, since your opponent isn't worse than you are.
The thing is just, how often does this actually happen? The people who play for a draw with White GENERALLY are weaker players than you are (last round in a tournament is basically the only exception).
Weaker players you certainly can beat in almost any position, as they WILL make mistakes somewhere. The Berlin Endgame, which would be a position they don't know well and which is just one large imbalance IMO looks like something that would make this easier than most other positions.
Usually, your opponent is going to play chess because he enjoys playing chess. And usually, "enjoys playing chess" doesn't mean that he tries to just pass for 50 moves as White until you accept his draw offer.
The only real case of "This guy is trying to draw with White" I ever run into are 70+ year olds, rated 1400-1500, who've been playing chess for 60 years and aren't really playing anymore, but just going through the motions.
Everyone else, even if they're a 900 rated kid who'd faint if they actually took a half point off me, at least tries their best to "play the position"; ie - push pawns when it's called for, etc (ok, a 900 rated kid will just do random shit, but you get what I mean)