Assisting as best as possible.
I'm doing the same project here, hope I can help ya in any way possible!
I've been searching every nook n cranny of the internet to get reference pics as well. Sadly I never found a single pic of his back till I found your thread... Anyways, I was looking at how difficult the helmet build might be as well and I think the best results will come from a pepakura model. Unfortunately, there isn't one for Zer0. So I'm working to develop one that will work. The front glass piece on mine will be made out of shaped plexiglass using a vacuum sealer and spray painted with window tint.
Only problem I've ran into thus far was finding the material for his first layer of the outfit. It has a light hectagon pattern to it and apparently that doesn't exist in the real world. So I went with a material used for swim wear thats elastic. Curious what your using for the outfit material.
Also, I found reference pictures online of the sword. I can post those on here if you'd like.