I am holding back on judging JH for this incident as I do think it sounds like the boy might have been misbehaving and JH could have reacted in anger to push the boy away from another child in the room that was maybe getting covered in the spray, having trouble breathing or got the spray in their eyes. In that situation I would be annoyed.
From the description of the charge it sounds like JH may have raised his voice/shouted and also maybe sworn at the child. If the incident was something like the spray affecting another child, then I would shout too, though I would avoid the swear words, and especially not direct swear words or derogatory comments to a child (I would say that's stupid behavior rather than tell the child they are stupid, for example).
I also think there's a story here of a man who's concerned about that home (with EG and JH) not being a suitable/safe place for his children, he's seen his child with a bruise, asked carefully how the child got the bruise, and he's chosen to prioritize his children's safety and report this to the police.
I sincerely hope that JH did not observe EG treating Lucas badly and giving Lucas those bruises. I hope she did those things behind JH's back and when he was out of town. I hope JH didn't treat Lucas the same way. If JH had a habit of treating the boys this way I'd be surprised that their father wouldn't have complained about it? The relatives who reported abuse in NM only said they suspected EG of abusing Lucas. In the write-up complaints it was said that Lucas was saying EG was mean to him, mistreating him, nothing was said about JH. When Lucas told his relatives those things I would be very surprised if they hadn't asked Lucas if his dad had been doing similar things to him. I would also think they might have asked Lucas, "where was your daddy when this happened?" to find out if JH was in the house, in the same room, or if he was out of town at the time?