The Golden Rule
Above all, enjoy and have fun. If you feel a rule needs modifying or you get something wrong, don't worry and do what is best for your game.
If playing multiplayer, make sure you agree on any changes you have made before you play.
After playing the stairs card I ended up reaching a dead end with no other possible paths to go other than back to the stairs card.
What do I do when this happens?
The official rules state that the Stairs Card now acts as your new entrance card, so you may return to the town from this point, although you wouldn't level up.
There are ways to minimise this risk using the face up map deck, but for those who find this rule frustrating, an alternative would be to either put the deadend into the face up map deck (just this once), or reshuffle the map deck and start again from the Stairs card.
How do I gain a level / Do I have to level up?
Your character gains a level once you reach the exit card from the lower level of a dungeon after playing the stairs card. You do not have to level up, but you won't gain the extra abilities, advantages (or disadvantages) for doing so.
Do I monsters get discarded once defeated?
You can fight the same type of monster multiple times in a dungeon, once you defeat a monster, you will meet the same type of monster is you roll the same number on the encounter table. The dungeon does not get easier the more you explore!
How do Sages get spells?
The "Hexes" and "Sorcery" skill cards allow characters to gain spells. Once you have a "Guildhouse" in your town, you can spend 5 coins to learn one of these skills (you aren't allowed both Hexes and Sorcery). Then you may pick and choose spell cards!
While in the town, if you buy buildings that bring new cards in play like the notice board or merchant, should I draw the initial cards for those buildings at the moment I buy them, or should I wait until I come back from another dungeon?
Draw the cards when you buy the building. Once in play defer to the leaving and entering the dungeon timings.