>Can i switch on forcepae via the terminal, once i am in the live session?
No, it's a parameter for the kernel. Once you've booted up it's too late.Try holding Shift to get to the grub menu. It should offer you a way to edit the kernel parameters.
Looking at this https://www.kernel.org/doc/Documentation/kernel-parameters.txt I get the impression forcepae only works on 32 bit.
