How can I consistently clear the final boss?

I’m at a point where I feel like I have almost mastered the first three layers. I never die or even use death defiances in the first two layers and I may lose a death defiance on Perseus but that’s it. I get to Hades every single run. However I beat him maybe one of every ten times. I have tried a LOT of times but cannot beat him consistently. The fight is so much longer than other fights and I just don’t have the endurance to be perfect for that long.

What can I do to try to get better at this? I go in with max defiances every time and he just shellacks me.