cynindesign wrote: I believe if I press the power button, it will disconnect the call....although I think there's a setting where I selected that option. If the number pad comes back on, will it stay there?

Check the "Accessibility" section of the main phone settings for using the power button to disconnect the call option.

The proximity sensor can/will turn off the screen during a call if it is covered.  Also the screen timeout will also shut off the screen.