1700 v 1400 0-1 Caro-Kann - any feedback?

Hi,
if you look at my games, you will see that I am full of blunders when I play at lunchtime in the office. Tonight I took plenty of time and managed to win this game with black.
Obviously I profited from white not defending the pawn @move 16 and the fork @move 40.
I would really appreciate feedback along three main lines:
1) Was there any situation where I "underplayed" my position?
2) Any explanation why
a) @move 21 the fork would have been fine? I discarded it because of Rxc8 and I cannot really see where the +2 comes from that stockfish attributes to the fork.
b) @move 25 and 27 advantage suddenly drops to +-0 although I am still a pawn up?
3) Do you think that the "endgame" classification was accurate at this point (move 21)? For me it definitely felt like midgame until something like move 32-36.

Thanks in advance :-)

1) Was there any situation where I "underplayed" my position?
14...Rac8 is the wrong rook. The rook at a8 is more useful than the rook at f8, as the rook at a8 supports the break ...a5. The rook at f8 does nothing useful.
2) Any explanation why
a) @move 21 the fork would have been fine? I discarded it because of Rxc8 and I cannot really see where the +2 comes from that stockfish attributes to the fork.
It is a pseudo fork as white indeed can save his rooks. However, you end up with a pawn more and more active pieces, which explains the +2: 1 from the pawn and 1 from activity. If you are a pawn up, then you should trade rooks if you can, as rook endings with 1 pawn up are often draw.
b) @move 25 and 27 advantage suddenly drops to +-0 although I am still a pawn up?
With your passive play you allowed him to play 28 Rc7. In rook endings an active rook is often worth a pawn. Hence his active rook nullifies your pawn up.
3) Do you think that the "endgame" classification was accurate at this point (move 21)? For me it definitely felt like midgame until something like move 32-36.
What is in a name...? It is an endgame as the main aim is not to checkmate the opposing king, but rather to queen your d-pawn.

@tpr Thanks for your comments. I see the points about move 14 and move 25 (I guess its the old rule "Rather do something with a piece doing nothing than do more with a piece already doing something.")