You may want to consider plastic culvert for the hoops, cut to a reasonable width, perhaps 2" or 2 1/2". Culvert diameter is whatever you desire. Not that difficult to cut with a common hand-saw.
Cut the hoops wide enough, then cut a hole in the middle with a hole saw, something like 3/4" or 1". Use threaded PVC fittings (Male through the hole, nut threaded inside the hoop), then PVC pipe for the rod.
Great idea using rebar stake. Slide PVC over the stake. Cheap, flexible, durable, lightweight. I'm unsure how well the culvert would handle high temps; should do reasonably well. El wire on the poles? Paintable, as well.
With that height, how do you intend to manage the drape of the cloth?
I look forward to seeing it.