Tips for Torturer's Dungeon?

A jolly good day to all of you fair travelers, honestly, watching videos vs actually doing TD was a horrific experience to say the least.

I do not understand why every 10 seconds or so, mobs start spawning, usually 2 sufferers and 1 axe thrower, or a sufferer and a axe thrower/priestess. The same goes for the puzzle, but from tutorials all it says is to clear rooms and interact with the iron maiden caskets in each room, but honestly even after watching and prepping, it still was not enough.

Any tips for a 1st timer?