As for the barbara 'incident',
i don't think he sexually assaulted her (rape). His aides might have, but it remains to be seen whether there was time for such a thing. who knows.
The reason why I think Joker has not done such a thing is because i think his corrupted mind does not embrace women in a potentially sexual way.
The only reason i can think of why he is attracted to Harley is because he turned her crazy and she's more or less a fellow mind like him (chaos).
If we were to take Jeanie's story as canon, then this tells us we have a joker that used to be a 'normal' man that lost everything. He obviously cared for jeanie. He lost her due to a corrupt police officer that set the house on fire because he wanted to back out of a mob attack on Ace chemicals, to obligate him into continuing with the plan.
He quit his job at ACE, then tried to become a comedian but fails horribly, no money, wife and kid, tries to better the situation by doing something bad and dangerous, his wife warns him not to do it because of the mob,
he then goes out to back out of the deal, then they kill his family - he'll see it all as his fault because he 1. quit. 2. got them in trouble. 3. initiated the deal. 4. wanted to back out.
having the burden of total family loss and his own personal world collapsing, has to continue with the break-in @ his former job,
and then, complete chaos erupts as the plan, like his own plan, falls to pieces and in a gunshooting it gets even worse; Batman appears in front of him, he's involved, and he knows he can't escape the bat-justice resulting in prison. still tries to escape but falls into the vat with chemicals.
left for dead, he manages to get out only to find he's disfigured due to the chemicals. completing the psychological damage done to him with physical damage done.
result? psychological insanity. he probably sees his life and everything that happened as a big joke. he blames himself for the death of his love, and he blames the mob and the police for how everything panned out. Hate for the (corrupt) police that killed his wife, hate for the mob that initiated his wife's death and the break-in, and in the chaos the plan breaks apart, and finally Batman whom he'll hate for being the one to fall into the chems and disfigure him. HE'll probably hold a grudge that he did come to the ACE break-in but not saved his wife and baby.
I think joker won't touch another woman because of Jeanie.