It uses QueryPerformanceCounter and QueryPerformanceFrequency.
If you have timer problems, you might wanna check that HPET (High Precision Event Timer) is enabled in your BIOS and in the OS (http://www.neowin.net/forum/topic/1075781-tweak-enable-hpet-in-bios-and-os-for-better-performance-and-fps/).
Did you already read about the Windows 8 RTC bug?
Would you consider, to force hardware-clock(HPET & ACPI Timer) to all Players with the c-rpg Mod?
No, but from what I read it happens only when you change bus frequency.
Variable, but it's running at 120 FPS unless under very heavy load.120 is pretty good.
Altering critical system settings is something a game should never, ever do.