about anything much at all. He may have previously told his cousin about the charming young lady he met in the Autumn without expecting to see her at Hunsford. But consult about the proposal? No, he just wouldn't do it. He has much too much confidence in his own 'superiority of mind' and would be well aware that his family would disapprove. His cousin might be sympathetic but I doubt that Darcy ever thought he needed Colonel Fitzwilliam's advice.

I think Austen is quite clear that Darcy's behaviour offends many people. He may be honest in his dealings, but he is arrogant and careless of other people's feelings. The 'cold politeness' Austen mentions can be very intimidating. A gentleman was expected to have more consideration of the feelings of others.
Elizabeth's furious response is quite natural given the great provocation Darcy provides. Tears and agitation are a normal reaction after such a scene.