Welcome to FT.

Your experience was definitely unfortunate, and there is a good reason those old 767-200s are now residing somewhere in the Mojave desert. But in my humble opinion, 20,000 AAdvantage miles does seem fair in this instance given the nature of the problem and the flight it took place on (JFK-SFO, NOT JFK-FCO). I'm sure some of the other members of the AA forum might have a vastly different opinion.

That said, you could always press on to see if you get more compensation.