Please help, this is horrible

The emaciated fire belly i posted about before got worse overnight, after refusing food for a week. He could no longer move by himself or get to the surface to breathe. I put him in a shallower area of the tank and tried to encourage him to eat, keeping an eye on him all day, but he got worse... then one of the females swam up and bit his leg off. While thrashing he seemed to break his spine as he folded in two. Bits of his innards were floating out from the hole where his leg was hanging off. He was clearly in too much pain to not put him out of his misery, but I didn't have any pure ethanol - only phenoxyethanol for euthanising fish. In a panic I put him in a 40% bath of phenoxyethanol. He immediately thrashed around for three to four seconds, then lay still for some time, before going stiff and rolling over.

Have I killed him? I have gently prodded him and he is stiff and unmoving. PLEASE tell me how badly I messed up here. I want to know if I made his passing worse or better. I really loved this little guy and lavished hours a day on trying to get him to eat, I'm so upset that it's ended like this and just want to know that he is out of his pain now.