My daughters Epileptic Dad, what rights does he have?

If he can prove adequate safety measures have been put in place for her, then he can. But your daughter has to know how to react to the seizure in that case (dialing 911, etc). Technically, since he has no one else with him and she's so young, you can require that he has visitation only under supervision. That means someone from a protective service would be there the whole time in case something happened.