Sorry for the delay, the answer is not simple and it took a bit to write down. What you are describing is called 'defamation', in this case business defamation. To prove defamation you need to show these 4 factors, which appear to exist:
1. A defamatory (untrue) statement
2. Of or concerning the plaintiff
3. Communicated to third parties AND
4. Damages (which are presumed when it is a business that is being defamed).
In addition you can claim that the other person is engaged in 'tortious interference with a business interest', send them a letter, and demand removal or you will file suit against them for losses. This is all against the individual, NOT against Facebook.
As far as Facebook is concerned, you need to leave a message and state that if they do not remove, they will be liable for defamation against you as well because under law ANYONE who repeats a defamatory statement is liable for damages as well, and demand that they remove or give over control of that page to you, since you are that business. I urge you to consider pursuing the past employee for the harm done, and do so concurrently while you are pursuing Facebook to remove this information posted against you.