The maximum z-level I can reach

You designate a garbage dump zone in only one tile using i-g.

Then you give the order to dump the stones you want to dump, or use mass dump: d-b-d. They will all be stored and forbidden on that one tile. To use them you'll have to unforbid them or use mass reclaim: d-b-c.

Any Dwarf associated with your Fortress can be taken by a mood. There are no restrictions based on age, profession or status (ie nobles).

Additionally a Moody dwarf will use his highest skill, or chosen randomly between high skills.

The following skills are available for selection:

• Armorsmith
• Bone carver
• Bowyer
• Carpenter
• Clothier
• Engraver
• Gem cutter
• Gem setter
• Glassmaker
• Leatherworker
• Mason
• Mechanic
• Metal crafter
• Metalsmith
• Miner
• Stone crafter
• Tanner
• Weaponsmith
• Weaver
• Wood crafter

Someone mentioned Legendary dwarves and populations under 20.

There have been recorded instances where populations under 20 did experience moods. Although Toady did mention in Dwarf Talk 7 this should never happen it has occurred in the wild.

Here is the quote from Toady:

It isn't a set time so much as a population. You need to have twenty dwarves, so if you're doing one of your smaller fortresses ... I don't remember if this is an init option or not right now, I think it's hardcoded twenty dwarves ... but if you're doing one of those hermit fortresses your hermit won't make an artifact. But once you get up to twenty dwarves, now this is not any twenty dwarves, they have to be twenty healthy dwarves that are capable of making an artifact - including those that have already made them, those don't count against the total - once you get up to twenty it just starts flipping coins at that point, and eventually it'll trigger the chance, it's completely when it happens.