Hi xtops,
I though you should use UEFI mode when using Windows... Are you really sure booting in BIOS mode?
From the installation guide:
So if you are booting System Rescue CD in a B&W screen well you are using UEFI and not BIOS mode.
Can you try first to mount your boot partition?
## EXAMPLE change sdc1 with your boot parition
sudo mount /dev/sdc1 /boot
## Then
sudo boot-update
It should work :-) Now if it is not working you should read the documentation again and follow UEFI (but first check in your BIOS if you are using UEFI or Legacy).
About the password, if it is not working I cannot really help for this, you should double check your keyboard layout, like maybe you were not typing in US layout of something like that. If you do not find your password back, I think you should re-install from the begining but I am not an expert here, maybe someone else can help you with this.
If I was you I would just forget Windows and use Funtoo, you will not regret ^^
Good luck and have fun ^^