Lead has a long biological half life and soluable salts can be absorbed through the skin. They also taste sweet, which could cause other problems. I'm reminded of the mention in Davis of the deaths caused by mercury snakes.Well, for one thing, lead acetate is cheaper. It's also less dangerous to handle, as long as you don't eat it, while aluminium dust is very harmful.
No, but it will react with oxygen in the air.Copper (I) is unstable and will naturally disproportionate to CuCl2 and Cu metal.
Atomic emission tends to be very narrow, observable linewidths tend to be dominated by doppler effects. Moleculer emission tends to happen in wider bands.They do not emit bands of light, rather discrete wavelengths.
Table seems to be missing some details, there are a lot of mentions elsewhere of bright bands for CuCl under 460nm but I can't find details.