on how to boot Ubuntu into the rough equivalent of Windows "safe mode".
If that seems to go well, yo could try bringing the system up as close to normally as possible except for X by editing the boot params again and adding "text"
to the boot params.
In any case, it makes sense to see if there are some old Xorg logs fro when it failed to come up. I'd take a peek in those to see if there is some other information that can be gleaned from those files.
Another useful approach (but kinda requires a bootable system or some knowledge of how to chroot into an exiting root filesystem or manually modifying the startup scripts, not too bad really) would be to configure the ssh server to come up and allow logging into the machine even in the case that X is off in the weeds.