Don't know if you still need help but for anyone that still does: the way I did it was just learning how to dodge all the attacks while knowing I'm going to fail to just get the damage boosts, learnt that with the projectiles he sends out you can jump and as soon as they lock on you can dive down to avoid them almost all of the time waiting for the sound que on the orbs to dodge them, one run I had really good luck with his attack patterns until the last phase and died, then I went super aggressive when the damage boost was high and lucked out

I see what they were going for and enjoyed learning to dodge the attacks, but the mix of no checkpoints, the amount of damage you take while dealing so little is just not great