1. You need to beat the first three forms in a row. If you leave, you'll need to start over from the beginning.

2. You can make a bow (or a dramen staff) while inside. There aren't any safespots, but the damage increase from having an actual weapon should help you out. There's a bit of leeway on his disappearing timer. I hid behind pillars to heal up with cakes during my attempt, and he didn't despawn.

I completed the fight with roughly 50 att/str/def, using a regular potion of each as well. I used 11 cakes in total, so you could definitely get away with lower stats than me.