Ah Floor 50. It's one of the hardest floor and first huge stop for many players. I don't exactly remember how I beat it but I had to make some weird team building (it's lost somewhere in this thread...)
I think you should stop right now and wait until you got more options. Floor 50 is a real challenge, despite being that low. Just come later, with other girls, more level, more amplues and better flower memories.

The warehouse should not reset. Instead, they add more stuff each time they add new floors.

And Crit activation is caped to 80%. Some girls can break it and reach 100% with specific buffs but you can't go above. Buff and debuff work separatly. and you won't be able to crit that boss, no matter what.