I was reading a short story and came across a vague part. Here is the part:
What she liked most about Ken Krieg? He didn’t mind she was taller or a volleyball star. Eating Buddhist cuisine in Buffalo, he told her flat as their food, “I want to marry you, work on Wall Street, and live in a mansion on Long Island.”
I have three questions. Firstly, what does "flat" mean exactly in this context? Secondly, as far as I understand "as their food" means "he told her flat when they eat food" But I am not sure if it is correct. Finally, what is the overall meaning of the bold one in quotes?