wait you're ahead of me again this cannot stand
I'm pretty sure you can literally just run straight past the FOEs on 8F to reach the room with the cow. They're far enough away that they can't reach you before you cross the floor to reach the cow's room. So fighting them was completely unnecessary, congrats on wasting your time.
And yeah, you should do the secret area on 16F next. Like, "why didn't you do it straight away" sort of next.
The fourth stratum boss is a pain in the arse (so like most bosses in these games, then), so good luck actually reaching the fifth stratum.