You don't owe them one thing. Nothing. If you want to make a profit, charge them a fee for the E & O. I know you do good work, so it will be easy money. Personally, I would try to recover some of my E & O annual fees if I were you, especially since you've wasted countless minutes, headaches and have been aggrevated repeatedly by them.
You could tell them: "Ya'll require E & O? Why would you assume I even have it, it's so expensive. If you want me to get it, it will be $750(or whatever, make em pay for a million dollar policy or even two) and when I'm approved, I'll forward it to you.
Before our fellow TNean Jim Plante got kicked off this board, he gave some of his normal great advice regarding E & O. . He said, "I neither admit or deny having E & O." You could try that.