[Celacena]

(I usually play on 'normal')
I am playing another game and got to the same point - by way of a warning - if Dema comes towards the party and starts up the stairs, you need to draw him back down to the area, otherwise he spawns too many nasties to deal with - I even take the risk of sacrificing an NPC to draw him down there - if you have enough kit in the bag of holding, you can nip outside, raise the NPC and re-equip to a reasonable level. if need be, you can rush a character in to pick up the dropped kit. With BoS and decent saving throws, you usually get to collect the original equipment with which you can go outside to re-equip (peace is needed for swapping armour)

I had a 6 person party (on solo multiplayer) and they all went up a few levels.

I also followed Von's example and did the tunnels better - I had a few hundred suits of armour to sell, but TBH couldn't be arsed to do so after I went over the 200k gp mark - there was nothing that I could spend that much cash on, so I abandoned the rest of the swords and armour.

you get much fewer dwarves if you nip outside and back in - orogs pretty much all the way. you need to make sure that you don't stray too far into the tunnel and get the slave-master as that ends the crop. you need to script a party properly to avoid mishaps - weaker party members with ranged weapons (without need for ammo) and tanks on scripts that don't have them chasing around too much. i was using a Monk as my main tank - the attacks per round of 9/2 dealt punishment swiftly. Monks really are one of the best fighter classes when they get past 20 - add the girdle of fire giant strength, ring of gaxx and ioun stone and you have a real bruiser.