How I did it? I just kept trying... I'm not sure but I think it took me about 10 to 15 in-game weeks. I managed to progress 2 levels per week maybe twice but other weeks he never showed up alone.
Either way I woke up before them every day and went to the bathroom at about 5:50-53. I noticed Nick joined mostly during work days, not the weekend. Also another thing that I kept doing was this, the night before I would stay in their room (so with Nick present obviously) after 23 so Julia would kick me out, then go to sleep right after. Thus, in the morning after the bath and before 7 am you get to catch Julia alone, masturbating on her bed which is one of those secret events. Again I have no idea if it had any connection but I did it anyway.
Some sprites weren't downloading with automatic updates, which caused some problems. This should fix the problem of freezing dialogs with Julia.
Fixed the bug when an event with Candy would stop too early and the players didn't get to see important story dialogs and events in the cafe.
Now Kate doesn't have to know Ruby to overhear her dialog with Andrew about the locked phone (event about breaking into principal's laptop).
My antivirus absolutely won't let me download the walkthrough. I get the game is fine and I can make an exception but still run it in the OS. But that walkthrough link from zippyshare is impossible to download. Like wtf? The walkthrough? My antivirus never did this before with anything!! What the hell is in that zippyshare link!?
No need to download the walkthrough. Just go down of the "download" page and the walkthrough will be right in front of you. Zoom in and read.
I myself finally thought of reading the last page of this walkthrough and was able to steal the damn key.
At the time of day for the event, there will be a wait button outside Nicolas' office. If you go and there is no wait button or message, try at another time. I think it was "after classes" so 15:00 - school close?