Four minutes under the broiler is a long time for a thin fillet, that's the real problem here. Set a timer for 2 minutes and check it, then flip and give it another 2. The smoke comes from fat and juices hitting the coil, so line the pan with foil and move the rack down a notch so the fish isn't right up against the heat. I've burned plenty of things and never once set off the alarm, so I wouldn't blame the broiler itself.

Misting does more than you're giving it credit for, just not in the way you measured. A hygrometer sitting a few feet away won't catch the microclimate right at the leaf surface, and that thin film of water does bump local humidity around the stomata for way longer than a few minutes. Pebble trays get dumped on constantly but they put out a steady trickle of moisture right under the canopy, which is exactly where the plant lives. The real fix for most people is air flow and watering habits, not a $40 machine that runs dry every other day.