Hello,
I am experienced nodejs developer, I can make your desktop recorder as you requested.
I can make 5 minute segment, and with nodejs terminal like, for very simple start, stop command.
As requested, i would use ffmpeg for recording, it is free and open source.
Unfortunately i don't have any live code to show you, but I assure you that I can deliver with pinpoint specification that you requested on time frame.
Contact me if you are interested