Strange behaviour in W10 after CRU and some other questions

[Hertz]

Hi guys!
So yesterday I overclocked my monitor (Dell U2713HM) from 720p@60Hz to 720p@120Hz (can go up to 130Hz).

Premise: my monitor is 1440p@60Hz, I play Battlefield 4 on 720 all low (GTX660) and wanted to see how 120hz feels...ok: it's amazing!

How it went:
tried a Custom Resolution with the nVidia Control Panel, all went nice and the test was passed (720p@120Hz); unfortunately there is no way to make it available to Battlefield 4. When in game 720p is selectable @59,81Hz.

Tried CRU (thank you for your work!): fast and easy to setup, the game recognize it and all works great. It's totally another experience but Windows 10 (AU done prior to this) is acting strange: just after boot and into the desktop the monitor goes black 3 or more times and you can hear the sound of plug-n-play each time then stabilize and all is up to normal. Why does this happens?

Now some other questions:

1. is it possibile to damage the monitor overclocking it?
2. why custom resolution created via nVidia Control Panel isn't available in game?
   

Thanks in advance and thanks to The Creator of this nice tool!