1. In labyrinth you can use both; maybe in part 3 post game.
You have disabled all skills except axe and beast on your save; sounds like you are confusing something.
As i already said; berserker job already has passive berserk. And you cant stack it so passive ability high berserker and frienzy mask is not needed; try to pay attention. The screenshot is from
your save. With removed all skills in ability menu and equipment.
View attachment 707786
It is normal; enemy accuracy was increased in part 2