OP make sure you do this, it is incredibly important. I was in a similar situation with a real dick of a co-founder who constantly pulled these bait and switch tactics. I would even go so far as to write down behaviors they exhibit and times where they tried to strong arm you in the past. Keep logs of everything, insist on communicating through means by which you can record the conversation. Writing things down may not stop their behavior, but it will seriously help your case should this turn into a legal fight.