I think the "mill target player" clause is just a more flexible selfmill mode. The few times you actually have enough mill kill your opponent in the late game it's nice to have it.
"Until end of turn, you may attack with creatures you control as though they had haste." does that do it
Depends on the number of artifact and enchantment creatures in your cube I would say. Exiling two creatures for five mana is pretty brutal, exiling a creature and another permanent seems more fair. You can also make it a sorcery, instants usually have to be slightly more expensive.but would it be nuts at 5?