That armor is FX or FX recast. You can tell by the shape of the back, the oversized helmet with the separate vocoder piece, etc. As a result it is most likely ABS. If it isn't painted, then I'd say it is certainly ABS. Good call on replacing the helmet
As for the pouch, I would simply drill out the rivet from behind. Then I would cut off the tool pouch from the rest of the pack. It will make a really nice-looking shoulder pouch after that.
The binocs would be cool. Just realize that they are not officially allowed as an accessory for this costume. That simply means that you want to keep it out of your approval photos and Specialist application. Otherwise it will be neat to carry those around.