Reverse prayer is fairly common in BDSM art, but this specific height doesn’t usually get called out because it is possible IRL. Double jointed people are capable of this, and of holding it for sustained periods without too much discomfort. The main issue is whether the rigger (aka rope tying person) has enough experience to know how to junction the points correctly, so the sub can still have enough freedom of movement to not constrict blood flow while staying tight enough to leave marks or not. After that you can concentrate on type of bind, whether you’re going to stay on the ground or do suspension work, breathplay, etc. Hopefully that discussion would have been held before anyone started getting tied up.
The cardboard box, elven wand, and tiara are three of the cheapest items in the game, so just dressing her in cheap crap is an effective way of scaling her damage. The actual effects of the items aren't relevant compared to the extra hits she gains just by wearing them.
I'd say the elven wand and kunai is pretty good, tiara is so so (she can't benefit from it on her own) and the cardboard box is overshadowed by the crown of thorns. It is only 1 coin more and it gives skill damage in addition to the def. Also rusty awl is actually the cheapest item but I don't see you mention it
