if you are going to bother with sleepers, you are creating a space for a drain! Just lay down a 1 inch pvc pipe that comes up through the plywood. Then lay down 2x2 sleepers with foam in between, Put it near the wall somewhere and go through the wall and into a trench right over the edge of the concrete slab. Dig out a hole for it a foot below the frost line and fill it with rocks. You don’t have any drop so it’s important to keep everything really short. You can always add some heating tape outside if it freezes. A working drain just for liquids can be really handy so you don’t have to carry a bucket outside,
That 1 inch ridgid foam they have now at all the home improvement stores is terrific. You no longer have to frame in a wall to insulate it. Just use the 4x8 sheets of foam.
Have you thought about changing to a sunlight-permiable roof? That’s free light! Clear plastic with a very light coat of white paint on it still transmits light and is private. Unfortunately it also leaks light at night.