Please critique my game (Caro-Kann, Fantasy variation) I'm an avid player of the caro-kann, yet I recently came across the Fantasy Variation for the first time. Although I won, I wanted to post my game for review:

[FEN ""]
[White ""]
[Black "Bad_Bishop"]

1. e4 c6 2. d4 d5 3. f3 Qb6 4. Nc3 dxe4 5. fxe4 e5 6. Nce2 {I knew we came out of book here, but I didn't know how to exploit it. I ended up trading pawns as my e-pawn was hanging} exd4 7. Nxd4 Bc5 8. c3 (8. Nde2?? {This simple line is interesting, as it shows the pressure on white's game even at an early stage} Bf2+ 9. Kd2 Qe3#) Nf6 9. e5 Bg4 {This move helps develop my queenside, as well as trading down against the isolated d-pawn} 10. Be2 Bxe2 11. Ngxe2 Nd5 12. Rf1? {White begins a kingside attack when his king is still stuck in the middle} O-O 13. h4 Nd7 {I wanted to open the centre and attack white's king. This move aims to either win the e-pawn, or provoke e6} 14. e6 fxe6 15. Nxe6 Rxf1+ 16. Kxf1 Be3? {My eyes lit up when I saw the possibility of a knight fork on e3, but there is no way to force it. My thinking here was just to lay a cheapo trap and hope for the best} 17. N2d4 (17. Bxe3?? Nxe3+) N7f6 (17...c5 {Immediately after playing 17...N7f6 I saw 17...c5 instead, but I don't think it works here} 18. Nxg7 Kxg7?! 19. Qg4+) 18. g4? Bxc1 {OK, it turns out 16...Be3 wasn't so poor, as I can remove the defender of g4 and win a pawn} 19. Qxc1 Nxg4 20. Qg5 {From this stage of the game, white is treatening mate, so almost all of the following moves have to be checks} Nde3+ 21. Ke2 Qxb2+ 22. Kd3 g6 23. Qe7 {I missed this move, as I thought white would play 23. Rg1} Qxc3+ {Forced, intending to trade queens and win a pawn} 24. Ke4 (24. Kxc3 Nd5+ {White should have opted for an inferior endgame rather than letting his king be pulled up the board}) Nf2+ 25. Ke5 (25. Kf3 Nd5+ {This shows the difficulty white is in. He either faces mate or large material losses}) Nc4+ 26. Kf4 (26. Kf6 Ne4#) Qe3#


My questions are:


How could black have played better?
I played 16...Be3 as a 'cheapo', which my opponent didn't fall for. What would have been better than 16...Be3?
On move 6, I'm not really sure why White didn't just play Nf3. After that, Black should play exd4 Qxd4 followed by (after Qxd4 Nxd4) just Bc5.

After Nce2, well surely exd4 makes sense, but I think Nf6 should have been considered, attacking the e4 pawn. Notice that anytime dxe5? is played then you have Bc5, with that mate threat that you already diagrammed (Bf2+ Kd2 Qe3#), so therefore you didn't have to give up the tension so early with dxe4. Nf6 develops and attacks e4 which is a critical point (a critical point is an unprotected piece/pawn or a piece/pawn with the same number of defenders and attackers on it. A critical point can also be a king or just like in the caters somewhere where you have weak squares and stuff. Attacking critical points is a key concept in torturing opponents or putting pressure in strategic chess).

By the way, I think Be3 is a medium good move... You are establishing a piece on the enemy's third rank or your sixth rank, which can be so strong in some middlegame positions that it is worth sacrificing an exchange for that piece and a pawn or something. The only other move I can think of is Re8, because there is a critical construction on the e-file with 2 knights on the e-file. 

A critical construction is a rank, file, or diagonal where there are 2 or more pieces in opposition or just like a lot of pieces (regardless of color) on the same rank/file/diagonal. Critical constructions are very good for finding important tactics or defensive tactical resources that can involve double attacks, skewers, interference, etc. Therefore I think Re8 instead of Be3 makes a lot of sense. You are creating a lot of tension on the two knights and activating the rook.

Here is a sample line. 16...Re8 17. Nxc5 Nxc5 18. Nd4 Qa6+ 19. Kg1 (all other moves like Kf2 and c4 are just a worse version) Qd3 20. Bd2 (Qxd3? Nxd3 and now you are attacking 2 critical points which is the b2 pawn and c1 bishop, and you can take advantage of the critical construction on the second rank with Re2. On top of that, your knights easily get to the sixth rank or other strong squares) Ne4 21. Be1 Qe3+ 22. Kh1?! (Kh2 is just more accurate) Bxf2 23. Qxf2 and this should win, and all of White's lines were backed up by an engine. 

P.s. On move 18 you missed ...c5, removing the defender of e6.

P.s. I think understanding critical points is something you mind as well learn anyway, and a technically possible answer to how you could have played this better. I think the opening was fine but you should have played Nf6 instead of exd4, because Nf6 develops while attacking a critical point which is e4, and you have a strong critical construction on the c5-g1 diagonal and tactical pattern if dxe5 which allows Bc5 and stuff.