Megaprojects or mod in more invaders
/thread
How does this answer the question in the OP??
Now for my question to the OP: did you have any meeting areas assigned from objects (i.e. table, cage, statue, well etc)?
If so you could have had too many dwarves attending parties instead of doing what they are supposed to. Another possibility is that you simply had too many dwarves doing stuff and not enough haulers, but the 30 idle dwarves kind of makes me lean toward the party scenario.
Mega projects are what keep my dwarf's busy, especially when there's no real work to be had. Start small, begin with building some sort of wall around your fortress. It's practical, trains your masons and helps with those cluttered stones.
ANYWAY, a real answer to the OP's question.
If you want a nicely organized fortress, you need to plan certain things before you start digging. Also on a note, seeds of all type are stored in one bag only; plump helmet seeds go in the plump helmet bag, sunshine seeds go in the sunshine seed bag, etc. Simply designate a custom stockpile for seeds next to your farms, and make sure the stockpile is specific to what you're growing; the dwarf's will also place the seeds in a barrel if you designate one to be used.
If you don't know how to make specific stockpiles, there is a
dwarfwiki article for that
Alternatively, you can just cook the useless seeds. That's what I do with all above ground plant seeds (except sunshine). Also, cooking helps with the clutter of food.
As for the running out of bags part, simply create a chain for creating pigtails, the dwarf version of hemp.
-Pigtail can only be grown during autumn and summer
-You will need a farmer's workshop to extract the plant fibers, this requires the thresher's skill
-After that you will need create a loom this requires the weaver's skill
-After your weaver has created the cloth, you need a clothier's shop to create bags (skill is obvious)
This little cycle can easily keep half a dozen dwarf's on work even on a small scale! If you want to make things more lucrative, you can create dyes as well. You'll need a quern for that (if you want a more laborious process) or you could construct a wind mill.
It will also help to name your dwarf's profession. Nothing fancy, for example, a mason and carpenter I call him "Furniturer." A stone/leather/wood, just abbreviate it! STN/WD/LTH Crft, using these methods will help you organize labor pool. Also, press 'j' to look at all the current jobs on que.
ANOTHER THING, soap was bugged previous versions. Sometimes when building the workshop, the ablity to mandate soap bars did not appear on the workshop when selected. You had to manually order it from the jobs que ('j'). Just type in soap from the job que, it should appear there.
As for the autopsy of your fort... I have no idea. Managing a 30 population is easy as hell. You really did not mention anything specific to what could've lead your fort to becoming sloth fortress, besides those bags.
edit: Did I mention adding more invaders equals more fun! Well, I did now!