I think N c7 ch K d8would have been better than Nxa7. Then follw by getting rooks connected . You had a tremendous position. It looks like a mate in 5 or 6 moves at leat you would cause much commotion such as by B a7
out. Thank you for showing the game.
on move 35, you don't have a bad pawn structure. its a pawn barrier, instead you should have sacrificed one of those pawns to create a outside passed pawn and queen it, but before that do a rook trade.
Everything else being equal, the most important thing in rook and pawn endgames are 1) Rook activity 2) King activity and last is pawns.
It's great you want to get a passed pawn with a5 (which is usually first priority in many endings), but if you improve your rook and king first I think white is close to winning.
Or Kd4-d5 first as the rook isn't too bad on Re4
17...Rhe1 looks interesting. It lines up the rook with the opponent's king. And the black knight is unprotected. If 18. Nf2 then 18...Bf3+ and 19...Rd2 would trap the knight. If the knight moves elsewhere then you have a nice attack with 18. Ba6 winning the exchange. If 18. f5 then it looks like you can win at least another pawn with 18...Bd3 which attacks the knight twice. This is just a quick observation. :)
My horrible endgame costs me the match, despite the aggressive gambit being successful.