1. That's the address contained within the on_esc pointer. The number itself is not of interest. But that the number is different than 0 clearly shows that on_esc is not NULL. Why don't you post your code so that we can have a look at this together?

2. Well there you have your proof that the plugin is causing fps slowdown. It's pretty hard to guess why this is the case as I don't have any information on the plugin. However, when you call a function inside a dll that needs a long time to return then this function either has to do complex calculations, just wastes time idling around or is forced to wait for an IO operation, e.g. a network activity.

3. That is not necessarily the case. See above at point 2. Additionally the plugin could set fps_max.