Maybe down this line? I’m not sure how I would approach a hard mode without making the game frustrating, especially the beginning where your options are so limited.
Well early on, the only issue is the vampirism bite, most of the early enemies aren't too tough if you can avoid getting bitten. The solution to making it more frustrating is to have holy water be more accessible early on, not too accessible, as you still want a challenge, but accessible enough that it's not insane difficulty, maybe Mila is given extra holy water early on, or there are more chests with holy water available in the early areas.