Safety of making PCBs
The developer is simply a dilute alkali, I use 12g of NaOH in a litre of water. It's quite safe but don't get it in your eyes and wash it off if you get it on the skin. Ferric chloride is quite safe, just wash it off if it gets on the skin. I always wear rubber gloves, both for protection and so that I can use hot etchant with manual agitation (I put the etchant and board in a small container in an old washing-up bowl with about 1" of just boiled water in it).

I've been making my own PCBs at home for about 40 years, using ferric chloride mostly. The only accident I've had that could have been serious was when I was walking across the room with an open bottle of conc. HCl in my hand, tripped, and a little splashed on my face next to an eye. I thought it might have got in the eye, but the fumes were bad enough. I immediately put my face under a tap and flushed the eye out for several minutes. It was sore for a few hours, but there was no damage.