What’s this attribute represented by a purple skull

Yes, you can even abuse it to stack stuff that is normally not stack-able like wands in the crafting screen and then pull the stack out. If you then use the wand and it burns out, it'll look as if the entire stack is burned out, but if you unstack them again inside a crafting screen only the top one will be.

I haven't had any problems doing this with saving yet, but then I play with permadeath so I rarely save.

Some might consider this to be an exploit, but since this is a single player game it is up to you to decide if want to use this trick or not.

The Bad Weapon and Hands Full (the debuff for wielding two weapons without the Dual Weilding skill) do not affect any of your statistics, but instead cause a direct percentage loss to your damage output when using melee weapons.

Bad Weapon reduces damage by 28%.
Hands Full reduces damage by 36%.

I'm not sure how these stack (whether it's a straight 64% drop, or compounded ~54% drop).

_{See the Bad Weapon page on the wiki if you want confirmation.}