Haha, seems like we were playing and mapping at the same time.
I stumbled over the same issue, didnt see any exploit, but I basically just ignored the potions. The thing is, that once you get to level 5 you are completely healed, and that triggers the crazy hens which always kill you. It is however easily posible to get all 5 featghers:
Head East right from the start, through the secret, then around the corner through the secret wall to the feather in the northeast. Now go back through the secret wall, but don't go west. Instead go east and jump into the teleporter. That brings you back to the starting position. Now go south and collect the other 3.
However...even with 5 feathers I always die and I never got to level 6.
