windows 8.1 problems with optical drive and eject button

Does Windows Right-click and Eject work? Do you see an Apple Keyboard entry in Device Manager -> HID?

Does the Eject work properly when you are booted in OS X side?

There is a driver on BC6 drivers package called AppleODDInstaller.exe. Can you run it?

Yes. Can you run the executable? You may need to reboot.

In Device Manager, under View, there should also be a 'Show Hidden Devices...' checkbox. Check it and see what new devices show up.

The AppleODDInstaller64 you highlighted is the correct driver. It should be an exe file. If you double-click on it, it should probe and install the CD/DVD device. The overall BC driver installer requires a reboot. Since we are installing only a part of it, if the CD/DVD drive does not show up, a reboot should allow the device to be visible.

if it's mainly this one disc you need to read then it's pretty easy to take another computer and make the disc into an iso mount it as a drive and install it as if it was a disc in the drive.

Please execute the following two procedures before we consider other options.

Resetting the System Management Controller (SMC) on your Mac - Apple Support

How to Reset NVRAM on your Mac - Apple Support

Now log back into Windows and check.

Can you run the setup.exe from the Bootcamp folder and test?