What resolution do you use normally?
xrandr |grep \*
Then run
sudo hwinfo --framebuffer
and see what mode(s) correspond to the desired resolution. These are XXX to
be used below. Maybe the list does not contain the same resolution you use
normally but that cannot be helped, in that case, just pick at random.
You edited the wrong line, change the first line GRUB_DEFAULT=314 back to
GRUB_DEFAULT=0 and change GRUB_CMDLINE_LINUX_DEFAULT="splash quiet" to
GRUB_CMDLINE_LINUX_DEFAULT="splash quiet vga=XXX"
then
sudo update-grub
and boot.
