2:35 is 5:10 pace, and if you were able to do 8 with 1 min rest you were probably doing them a little faster than tempo pace but if done at 5k race pace would have been too hard to finish, so you were probably runnnig slower than 10k pace but faster than tempo pace is my guess.
i think you're probably definitely capable of breaking 16:30 for 5k right now, because 5:20 pace would feel a little easier than how fast you were doing those 800's. and when you're doing 8 half mile repeats, 1 min of rest doesnt feel like a whole lot.
if you go out and run a 5k on the roads or something, i would guess aiming for 5:20 for your opening mile and judge how you feel. if you're feeling good, up the pace to more like 5:10 pace, and if still feeling within the realm of completion at that pace one you get to the 2 mile mark, just start slowly pushing it more and more. i bet you're in 16:15-25 5k shape.