Restart until you spawn next to the exit room. Use Groton, because health will not matter. The boomerang effect will cause large Bosses to be hit multiple times upon each attack. Use it to clear enemies that may be spawned by Bosses. Also, the blowfish gun secondary weapon can be fired many times even with the starting ammo capacity and deals a decent amount of damage. However, do not fire it at targets that are too close.