I'm not so sure about this, CM.
I'm not talking about you resigning as chief of staff. I'm talking about you ending your friendship with Eric. I don't know what's going on. But it seems like you might be jumping too quickly to a conclusion that might not be totally valid. Maybe you should just stop for a second, sit back and think about whatever the situation is...lay on it for a while...talk to Eric personally, not just through his girlfriend. If you don't talk to Eric yourself, you shouldn't end the friendship based on someone else's word--to do so just means you aren't very trustworthy yourself, no offense intended.
If you talk to Eric, and he is uncooperative, then that's a different story. But, just based on what I know of him, I don't think he'll be uncooperative.