I had a few hard times planning my Disney wedding also, with the same thoughts of cancelling, even at the last minute, but have faith, something will work out for you. Disney have some strange policies, but they are the best at putting together a wedding. I am so glad I went ahead with our wedding at Disney and am so sad it's now in the past.
Could you not have the reception at one of Epcots outside locations, where it could last until midnight or 1am?
When we had our wedding we were told they would charge $400 per hour after 11pm for 'extra time'. Our reception was at the American Adventure parlour.
I guess though (although no excuse for bad manners), that they were amazed you wanted an off site reception, hence her frosty manners.
Good luck.