If your hero gets +1A this affects his profile.
This means that if he had 1A in his profile he now has 2A.
If he fights with 2 weapons, he will therefore get an extra +1, making it 3A in total.
You do NOT get a malus for fighting with your "off" hand. In fact, forget that off hand business. It's way to complicated.
If your hero wield 2 different weapons, you may decide which weapon strikes 2x and the other automatically strikes 1x
Hero has 2A in profile and wields 1 sword and 1 mace.
We use coloured dice to make it easier. You will roll, for instance, 2 black dice and 1 red dice. You may decide BEFORE YOU ROLL, what "black" and "red" stands for.
Either "black = sword" and "red = axe"