Knowing when to loose the exchange.

Knowing when to lose the exchange for the better position instead of piece value, is hard for beginners (myself included).

But if I did not take white's dark-squared bishop with my rook, I wouldn't have won, or at least saved my position.

To be honest the exchange sac was necessary here to prevent the loss. But you did get a better position
I would suggest Petrosian's games to learn more about exchange sacs

After 24 Rhf3 the exchange should prevail.
The exchange sacrifice offered good practical chances, but the position was already lost.