Right, the crying thing. 96% sure that Azzarello wrote it so you wouldn't know why he was crying, because its totally weird and is another way of alienating the Joker - like the fact the book isn't from the Joker's POV, because Azzarello thought it would take away the unpredictability of the character, since he's insane and whatnot.
Also, it comes right after the part where Jonny Jonny thinks he understands the Joker. And we all know how that turns out.
So yeah, its a good way of making him more complex.
Or he just totally misses his best buddy Basty, who has been a total bitch by ignoring his calls.
has he ever committed sexual crimes before?
Not that I can think of, its not really his MO. Unless it would be funny to him, like the above rape. Rape probably seems to obvious to him and it's a control thing anyways.