That doesn't even make sense. Whether your skin is spongy or not doesn't matter; it's molten lead, and people have been hitting you in the face continuously anyway. People and animals get lead poisoning just from touching lead. Besides the whole part with the fumes and the breathing and the oh look it's in your system now.
Having touched lead myself, I'm fairly certain that isn't the case. Either that, or my father was negligent by not giving (and himself wearing) gloves. And his warnings about not touching mucous membranes* until washing hands was meaningless.
*Not his exact words.
The fumes...you have a point there.
About leaden scales melting: It doesn't really matter if it does damage, as it removes the armour value of the scales, effectively reducing health by making future hits matter more.
The game doesn't work like that.
...Or, at least, it didn't when there were discrete mechanics for damage.