Been doing all of that. Except the potions, they're not useful. It takes one turn to heal ~20HP and the next attack takes 50 or 60 HP, so it's a net loss every time.
It's easy to get slaughtered within just a couple turns when the solo hero goes up against one Plague Plant and two Lurker Snakes, which is a lot of the mandatory fights in the Lv5 cave.
I hope in the future you can find a way to rebalance things, give us a second hero earlier, or add difficulty select menu.