?? What size fish you going for ?? For years I used a single burner Camping Gaz thing + an old saucepan to melt the lead and I made weights up to a couple of pounds for wreck fishing?
Unless you want to mass produce weights of course but then probably you only have a limited number of moulds anyway.
5 Precepts of Buddhism seem appropriate. Refrain from taking life. Refrain from taking that which is not given. Refrain from misconduct. Refrain from lying. Refrain from intoxicants which lead to loss of mindfulness