The boss in Stage 1 is as the same as Stage 3 here.
The boss of stage 5 is as the same as Stage 3, just that there are 2 of them with no sidekicks.
I suggest we bring in the green dispel potion. Place two Dark heroes in your team. With a team like mine here, 3.1K is not all that hard. Except for the Antidote, I did not use any fancy battle item. If you bring in a healer, perhaps you would need to bring in the mana potion, just in case the board does not work for you.