may be you can mount your files/partition in read-write mode using some rescue CD and then edit them.... (say /etc/X11/xorg.conf, etc)
Also check out /etc/inittab file for setting default runlevel to text mode or to graphical login.
No idea about flickering monitor

could that be driver problem or incompatible hardware issues :-/ I have never faced such a thing before (thankfully !!)
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regards