There is no far enough! You can look everyday and go as far out as you can and you may luck up and get some dates. It's very difficult. It's the same way as Topsail. Keep in mind, they have implemented free day passes for people. They clog up the entrance and take over the amenities, mostly at Topsail. Beach goer traffic is now very heavy. It use to be you had a little more seclusion on the beach when you camper but no more. The beaches at these campgrounds are now packed! Pools, showers etc..

Depends on your needs and time of the year for your stay. As many have said, sooner is better.

We made our reservations almost a year in advance.

Florida State Parks allow reservations up to 11 months in advance. For the popular parks like this one, you should book that far in advance if possible. But there's always a chance you can find a cancellation later if you didn't reserve that far in advance.

Busy place. Earliest possible via their online portal. I really don't know the details of how often they have vacancy but the park is beautiful but not that large so I imagine high demand.