I don't... see a difficulty setting anywhere. Only settings to prevent the world going into hardmode, or restricting what kind of player could join. (softcore vs mediumcore etc.)
Yep, they do. The 490V reading is still slightly above my stated off load spec, but it might be because your mains output is slightly higher. Sometimes my mains outputs as much as 124VAC when it is suppose to be 117VAC.