Shouldn't be any closer than you should get to a car.
Yes, yes, yes, but back in the real world, people do. There's a difference between what people should do and what actually happens.
There should have been 20 coppers at the station waiting to respond to the situation in an ideal world, but back in the real world there wasn't.
With regards to the actual incident, you've got to make a judgement with regards to your safety and respond accordingly - the white van man was driving aggressively, so was likely to act aggressively when someone reacted to the tool, as he subsequently did.
In short, it's not worth getting into a fight over, or damaging your bike for, despite what the STW Justice League™ may advocate.
The OP's wife could have quietly and discreetly taken his numberplate, while taking an alternative route for the rest of the journey. Then report the fella.
I've been in plenty of scrapes on the commute, and apart from venting a bit of spleen, no one gains from arguing in the road, as this thread demonstrates.
Unless you're a proper hard man, of course.