Watch a cockroach die after a shot of Raid. The roach isn't kicking, his muscles are spasming uncontrolably. That's how a person dies from nerve agent. So yes, you could potentially break your back. Skin boiling? No, that would be a blister agent. Very painful on the skin but even worse when inhaled. You develope blisters in your lungs and airway, these break, and you end up drowning in your own bodily fluids. If you can keep it external you'll probably live but you'll be in pure hell for awhile. And, no, chemical rounds are not really filled with little glass spheres in a string-of-pearls configuration