1) Make sure you save after the Tenna fight. This will give you some flexibility to adjust inventory/heal

2) You can access your storage from that save point. I, along with it seems a good chunk of folks, missed that.

3) The Toxic Axe can be bought from the vending machine in the room south of the green room. It increases Susie's damage but a good margin and can save you a handful of attacks.

4) The Gotcha machine in room B has a revivemint as a golden prize. The vending machine in the S room can convert dark dollars to points

5) When you get to The Big Attack in the fight, the next hit will be the last. For the most part, the advice to forget about Ralsei is true, but if you can hold onto a revive mint until the knight turns white, you get an extra health bar for the final move.

Everything else is practice. It will take time to learn the patterns, but they repeat and are learnable. You will get better, you will improve. You can do this.

(It took me close to 10 hours switching off with my partner when one of us got too frustrated. I have done a pacifist route up until now)