I don't know how helpful seeing this alternate game will be for you, as I'm still a student of this game myself, but I think it's beneficial to see how a game could be alternatively played, even if in this case I was doing both sides. Maybe if I ran it again from move #18 and worked harder at Black getting the edge, it might run differently. Just might try that if I have time or inclination.
Where did I go wrong?
Thanks for the help.
At 5. Rad1
I think a better response would be: 5...Bxh3
Aiming for 6...Bg4. Attacking the black queen. Anywhere the queen moves she will either be captured immediately or black will respond with 6... Nf3+ , forking the queen and king. The exception being 6. Qh1 Bf3, forking the queen and the rook. Either way white gets a valuable kingside pawn and wins the exchange.
I don't think you did a lot wrong. In fact, after 25. a3 (although you are a pawn down and maybe white's pieces are a bit more active) your position is not so bad. Certainly playable. However, in this position your pieces are a little cramped and in each other's way. The rook on f6 looks dangerously placed. The knight, were it not pinned, could go to h5 or e4, either of which could cause problems. Also, white is mounting a large attack on your king.
All things considered I think I would play 25. ... Bxg3. I can see why you played 25. ... Qd7. It potentially activates your rook on a8 and keeps the pressure on the c8-h2 diagonal. However, the pressure looks good but doesn't threaten much in reality because your bisjop and queen are the wrong way around. Also, Qd7 allows white to play Rad1 pinning the bishop.
After 25. ... Bxg3 I could imagine 26. Qxg3 Qf8 and then if you can get your rooks on a7 and f7 and your c7 pawn on c4 you would be hard to break down.
Going back to the line played (25. ... Qd7 26. Rad1) your 26. ... Bb3 doesn't really do much except remove your bishop from the main action. But 28. ... Be6 is the move that loses the game. You don't see the tactic that the black queen can take on f6 because the pawn is pinned. If you see this, then 28. ... Bxg3 (even now the exchange could help) followed by Rf7 holds everything together.
So in short, your opponent was on top, his position was a bit better than yours but you were still in the game. You lost mainly because of one blunder - 28. ... Be6.
Here is a game I played against a much higher rated player. I lost.
I'm still fairly happy with my performance, particularly throughout the opening and middle game, where I think that I was able to maintain equilibrium. But then the endgame came and although I was only a pawn down, I realized how exponentially better my opponents position was. If anybody cares to point out blunders or superior variations it would be greatly appreciated.
One Idea I had after-the-fact was:
18...Bd6 (Instead of...Nc4?, which destroyed my pawn structure.)
Protecting my Knight. As well as preparing a preliminary pin.
Aiming for 19...Bg4
20. hxg4 Nf3+ Forking the king and knight.
Thanks!