Pandora Box - Oh, I love that level, especially for the music. Only thing I dislike are those giant smiles with the one eye that you have to shoot - usually I just turn invisible with Kevin and run past them as quick as I can, if that's any help to you. There's a max amount of thick blood you can make into serum per level, so I'd suggest grinding until you reach that point and leveling up your characters before fighting the next boss. I'd tend to level up Dan, Kaede, and Coyote first, and worry about the rest later on in the game, but that's just me.
Did you face the boss, though? The rainbow guy with the afro? (Andrei Ulmeyda

) I had some trouble with him. I ended up using Con, and wore the stamina ring as it gives you double the health, though it is still easy to die pretty quickly if cornered by him. The trick to it is that you want him to come around a corner at you, and then try to get around the other side of him quickly so that you can shoot at his afro. I'm not kidding.
Hope you stick with it and have fun.
I believe I did fight the rainbow afro man because I was delight by the game with one of the weirdest images of my mind to date. But it's been a while since I played the level and I cannot remember it very well.