I'm afraid I'm about to repeat myself, but whatever. In no way did Fuchsia have a rocket explode in his face, or anywhere near enough for it to cause any damage to him whatsoever. For it to have been done so, the Archivist would have had to fire his web before the demon even fired his weapon, which would have been an interrupt. As it is, you stated that the Archivist launched his web as the rocket left the barrel, which means the two projectiles meet each-other halfway between the two combatants, unless you want to tell me the web is traveling at a higher velocity than the rocket. 

Assuming it doesn't, that means the two projectiles collide half-way between the two points of origin. 15 feet away from them both. An uncharged rocket does not have that kind of blast radius. Fuchsia is, at the time of the explosion, moving backwards at high speed. A charged attack does not transfer it's power onto the attack it meets. Charging your web once makes it hard as steel (or was it iron?) - And would damage the rocket enough to blow it up. If it wasn't charged, it would have been soft as leather. No?

The terrain is covered in snow and sand. The sand is either wet, frozen, or both.