My daughter and her husband are having marriage problems and my daughter is looking to move herself and her daughter to PA from Florida. She is worried that there is some kind of law that would cause her problems. There are no legal papers at this point. Just looking to separate for awhile.
Please advise.

At this time, absent any legal paperwork, either parent can take the child and go anywhere.

Can the father go to Court and request the return of the child, particularly if the living situation in Florida is not to his liking.

Living apart is a separation but not a legal separation. She can be divorced for abandonment if she just picks up and leaves.