If the hours of 9-5 are for the visitors center. If I wanted to just walk around the park, is it effectively open from dawn to dusk (based on the closing time's responses)?

Yes, but I would not recommend going at night because the visitor center can answer a lot of these type of questions and can entertain you during your visit.

Yep, dawn until dusk. Just make sure you're out of the park before the rangers lock the gates.

Yes, but visit the Visitor's Center if possible. They have a nice display to explain the battle.

Yes, you can go on the grounds and hike the trails & enjoy the beauty of MNB from dawn to dusk!