There are a few issues going on, with annoying behavior from both LR and FB:
- The LR builtin FB publishing service only exports LR's Title field, not LR's Caption field. This is a silly limitation of LR (see Re: Posting CAPTION to Facebook).
- FB shows for its caption the concatenation of LR's Title, Caption, and Copyright fields. There is no way to change FB's behavior here -- see Re: Lightroom Caption Export.
- LR always exports the Copyright field. There is no way built in to LR to change that.
One workaround is to use this third-party FB plugin instead -- the author has an excellent reputation.
To provide Adobe with feedback on this, post in the official feedback forum.