Thanks you guys!

I finally had the time to look through my tools (the slow drip was not forcing me to do anything quickly) and I found a deep socket that fit the bill (I mean, the nut) - 15/16". Better yet, the handle of the socket wrench was very long (actually an old-style torque wrench). Now, I understand the physics of torque = force x moment-arm, but I was still surprised at how easily the thing turned once I had the proper tools. So easily that I think I had to have loosened it with the crescent wrench. I mean, when I was using the crescent wrench, I seemed to be physically deforming the nut, with nothing budging.

Anyway, I was able to get the replacement cartridge at home despot (under $8) and the drip is no more. Yay!

-J