Is there an indoor space I could rent for an event with 20-30 people? Considering somewhere close to the beach with access to water and electricity, restrooms.

Pacific Ocean club, they have everything you look for.

Visit the fortmonroe.org web page, it will provide you with answers to your questions.

No. The public was not allowed in anywhere inside of the fort buildings.

Yes you can, just go to paradise ocean club on google & then go to Ft. Monroe on google as well because they also have RV sites there. FT Monroe is a decommissioned military post so anyone can go on.