strange... do you have done all of this only on TTY? (I ask you for be sure)
when you log into GUI, choose "session quit" and try again on tty, then
reboot (I have 3 computers and works)
Do you tried with sudo poweroff instead of reboot?
Maybe the problem is not this, (I'm not expert).
Do you have other de? Maybe lightdm is not setted as default desktop manager
[I'm NOT sure of this, I NOT recommend you] If all of this not work, you can
try to edit .bashrc and add the commands that remove or stop lightdm on boot
(I solved the blanking screen with this method), or trying in /etc/issue, but
I think there are solutions more elegant than these eheh
