1. Yes, there is a finite supply of SCP-500. The article states "SCP-500 is a small plastic can which at the time of writing contains forty-seven (47) red pills." So in that universe, there are 47 pills.
2. This may be because I am a professional idiot, with a bachelor's degree in stupidity, but I thought neutralized meant that the anomaly completely lost its anomalous properties. Which would make said anomaly no longer an SCP.