the lead poisoning thing will work quite differently and in fact will mostly be based on how galena dust during lead mining is extremely toxic
So if you mine lead ore(or even like raw lead block) without water being next to it it'll create a poisonous cloud
Lead ore should also naturally generate more next to water in caves.

The previous thing with lead things being in your hotbar should still be in config but turned off by default

making lead ore generate next to water will maybe be a bit more work, since there is no vanilla feature like that, everything else is pretty doable

Hmm okay i guess if it's too hard you can leave that for now, could you make it that this area effect cloud also has a bunch of smoke particles in? to resemble more dust from mining if that's possible