"It seems hopelessly naive to discuss your IP with another (much bigger) company in this way."
This is SOP for US corporations and has been since at least the time of Philo Farnsworth and even the patents of AG Bell (who had a very helpful lawyer with good friends in the USPO of the time).
Later there was the case of Ford and the intermittent wiper blade drive.
These are only the famous ones. You can bet there are plenty more out there. NCR comes to mind.