You will need at least a *Blacksmith* level 4 , not crafting to craft tenebrium weapons.
Crafting level 5 which will give you added *bonus* for your blacksmith, otherwise, you are good to go.
As for the rest of your question, I ran out of fun & willpower to continue my 2nd Act, so couldn't help you there.
I believe the Void monster, you can kill it later, something about destroying a stone first. (Don't want to spoil it for you, so I'll be vague)
