As an Infantryman I greatly appreciate my artillery support and will use it whenever needed. I do not appreciate yours, so just stop doing that!
Explosives used in any urban setting cause destruction, whether they are 12 pounder or 175mm shells, hand grenades, mortars, or anything else.
.303 tracer was in use by the British since 1914 and given the number of Irish who had already served in The War it's unlikely it would have been considered remarkable; I'm certain that troops at the front would have mentioned it in letters home. Besides (and trust me on this!) you really don't notice too much what sort of bullets are coming at you when YOU are the target and you're not under cover.
Frankly, I don't really give a hoot who set the fires. They existed, and this business of assigning blame a century later ranks with Daesh never forgetting how Richard massacred the Saracens at Acre in 1191.