Though i have to wonder how long he will be capable of remaining "sane"... remaining to be Lelouch. I am afraid the "Zero" part of his personality might become his actual one if he keeps this up.
Shirley hit close to home. Now he just had to shoot his "first love" (the only half-sibling he cared about), and to make matters worse - he has to "blackmail" Euphie in public to make her seem like a deceptive and evil Britanian bitch, staining her name and taking advantage of the fact... while he obviously knows that is as far away from the truth as possible, and all of it is his fault (even if unintentional, it won't stop him from blaming himself for all the mess) . I can only guess how damaging this must be to him.
While it is absolutely perfect for Zero, Lelouch would, probably, want to curl up in a dark corner and cry his eyes out (especially the geass one
). If he wouldn't have CC's shoulder to cry on, he would truly go insane. Now... what would happen to him if he is forced to kill Suzaku in the upcoming battle ? Then there is the student council... their deaths would affect Lulu as well.
^ Now, if he can "survive" all the above (assuming Suzaku or student council gets killed), i would assume he has a good chance of remaining sane. Though should anything happen to Nunnally, it would be the final nail in his coffin.
In short - i really fear for Lulu's sanity.