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Your opening analysis seems pretty good so I'll just skip to 20.Rac1. This is where the real game direction seems to be. The move you played I don't think is that good as it doesn't do anything. White has a clear weakness at c2 and it's a backward pawn. I would normally just build up on that weak pawn with something like 20....Rc7, but I kind of fear f4 if you were to play the other rook onto the c-file. So then what? I would like to make your bishop more useful at h6 for example which would require h5. I just don't see how you can make this work. Nf4 seems to be begging to be played, then doubling on the cfile seems a lot easier. You could potentially triple as well. If white doesn't take on f4 then you have h5 and bh6 and you are in business so I guess 20...Nf4 is the move I would suggest.
As played, he does you a favor by taking on d5. Your pawn center gets stronger and you definitely have plans for e4 which could really hurt if prepared for.
22...g5 seems inaccurate to me. Some rook is screaming to be played to e8. I would choose the c-rook. No need to kick his knight to a better square and weaken the white squares around your king. After 22..Rae8, you must be a little better.
23..nf4 allows him to kill your central pawn roller so that can't be right. I still play 23...Rce8 and believe the tactics favor you if he takes on e5. I could be wrong on that.
Your analysis after move 26 seems pretty accurate. You have all these weaknesses, doubled pawns etc. I'm too tired to delve too far into it but you have resources and advantages too. It's just not the type of position that i like as black.
After 40. g3, if only you could trade queens it would be an easy win. I don't see it though. If you could get your pawn rolling with queens on, maybe but I also don't see it. The white square weakness around your king looks too great. I guess it's a draw unless I'm missing something.