Apple - Boot into Mac from Windows after failed Bootcamp
The "correct answer" to this turn out to be not so deep. The wireless keyboard was not waking up fast enough on startup to get the key press to initiate any of the startup key combos.
Hitting a couple keys before hitting the power button on the mac mini allowed the keyboard to wake up first. All key combos work.
I believe the fact that the Bootcamp control panel does not show up on the Windows side, is because it is Windows 8 and Bootcamp and it's Windows support drivers are meant for Windows 7.
Also plugging the wireless keyboard into the mac also sped things up
I'm not sure how likely it is that drivers tampered with the EFI. That said, you have a few options.
You could try installing reFIT. This should bring up a boot menu regardless of your holding the Option key. You can find it here.
You could try resetting the System Management Controller. I don't know so much about it to veritably say that this is causing your issue, but it's worth a shot.
My first course of action, however, would be to get a FireWire cable and boot to FireWire Target Disk Mode by holding "T" during bootup on the stunted computer and hook it up to a working Mac. You can then try running disk integrity checks on it using Disk Utility as normal. You can even try selecting the boot disk on that computer and restarting to see if there's an actual file-level issue with the your operating system.
If your disk does not appear on the Mac you attach it to, you can't boot to FireWire Target Disk Mode, or you can't boot to the OS on the attached Mac (assuming the OS is compatible), you've got additional issues which you should come back and tell us about.
Turn off the mac, then when it is starting up again, hold the option key. This will bring up a menu that will allow to easily select which operating system to boot into.
After booting into OSX, you can go to Apple Menu -> System Preferences -> Startup Disk (Under System section) and change which OS to boot into by default.