Is my BootCamp-ed Windows seeing less VRAM than my Macbook (Pro, 13", mid-2014) actually has? If so, how can I make it see that it has more?
Windows can allocate as much video memory as the driver allows. So the problem is not really with Windows, but the driver that Apple provides for that system. Yes Apple wrote the Windows driver for bootcamp on your Mac.

I don't have specific experiences with this but I have heard of people going directly to the manufacturers web site and downloading the drivers for the specific version of Windows and the graphics card in your Mac. Often this will work for other system hardware as well.

The worst that should happen is that you'll have to boot into safe mode to remove the driver, assuming you can find it on Intel's web site and get it to install.