When business guys start saying "you can be replaced" or that they'll "start a competing company" the correct answer is /always/ "Fantastic! Please do, you'll make me look good.".

This guy was a clown playing for status. Where there's money there is always people playing like this. Focus on delivering value to the customers at a fair price and nothing else.

Also, if people are saying "You can be replaced" it means you can't be replaced and you're doing something right.

Maybe I missed this, but did you get a founders agreement put together? It's not a fun conversation, but it's worth nailing down at the very beginning.