AF is "Attack Frames", basically attack speed. It's the amount of frames it takes to perform an attack, so lower is better.
Do you plain to upload games on steam?
thanks for the question! I'm not planning to put games on steam at the moment. It costs a upload fee of 100$ which my little hobby can't afford right now. :)
Do damage stacks? for example I have an skull amulet of firebolt and a book of firebolt, giving me two icons.
that... would've been a cool thing to add. But no, they don't stack (it's just there to show you have two things that give you the same skill)