Of course you all realize that use of any copyrighted material on the internet (and elsewhere for that matter) is governed by the Fair Use Doctrine. If you use it ‘within reason’, you have nothing to worry about. What that exactly means, I don’t know, and would require another thread (to say nothing of several volumes of law books I’m sure).
EDIT: BTW you can rest assured my actions on this message board certainly conforms to the Fair Use Doctrine, at least to the best of my knowledge .
Terms don’t hold copyright protection. That would likely be a trademark.
You use the copyright symbol when you are the owner of a copyright and want to make it clear that a document is under copyright protection. There’s no reason for you to ever use a copyright symbol for someone else.
It isn’t and it wouldn’t be eligible (at least in US copyright law) because it does not meet the threshold of originality. (It is just the letter C in a circle.)