Based on your description, I would suggest to pull the front seam back up, spread some adhesive on the roof decking, and apply another piece of Eternabond to the seam. Do not staple the membrane, that will only cause holes in it.
If you place small plywood pieces and walk on them while installing the primer and finish coat, you won't need to be on the finished surface while the coatings are curing (although I wouldn't worry about that). You can move the pieces as you apply primer and the final coat. There is nothing to prevent you from doing the roof in sections other than the time and inconvenience involved. Either that or move a ladder along the side while using a roller and a pole extension. The latter would be my course of action but you'll still need to get up there to seal vent seams and wash the existing surface.
I'd suggest to go slow and be thorough. The coating systems are not a magic fix-all but will extend the lifetime of EPDM roofs and do lower interior temps.
Good luck!