I question why you need to have an anonymous email address to register for a forum when you can just make it private, and why you would feel the need to hide your email address from the administrators? I'd guess most people use a real email address in case they need to reset their password or want notifications, instead of going to extra trouble.

I question why you need to connect to these forums via vpn when they don't appear to release IP addresses, or why you would worry enough about them making an exception in your case.