You can modify this at any time during your journey, you don't have to start a new.
And yes just messing with your characters handful of stats and the AI's can make the game much more inline to what I feel a Hard should feel like. For example, the OP went heavy on NPC HP's which isn't bad, however depending on how you like to play that will make the game harder but the battle longer to. Another option is to give the AI more AP per round, that allows them more things they can do often. Yes to either up'ing AI Initiative or dropping your own Initiative down, when you are always in the front of the pecking order that makes the battle a lot easier, getting it inline where you can show up anywhere seems to be ideal for strategy.
OP since you now have done this, the next area to make changes if you were wanting to dig deeper yet would be reviewing and tweaking of spells. It has been improved in EE, but I think there is still room for improvement there.
