I usualy cap my population at 80 or 100, to save fps but also to not have to have a hard time finding everyone something to do.
As such, my forts usualy have only a few idlers. Soap/cheese/lye makers, peasant, and just about everything else I cant use I either draft into my army or add them to the masons, which are the only dwarves tasked with non-food hauling. I usualy have a only a few dwarves practising other crafts.
My glassmakers, stonecrafters, clothworkers or leatherworkers usualy dont to idle, as they constantly churn out building materials or merchant fodder. My metalworkers are all set to furnace opperating, so those rarely idle either even when I dont have any metal objects I need them to make.
About backlogs, I dont have much of those. All large task orders like block, craft, glass, etc. production is ordered by setting workshops on repeat with only a few orders, thus only creating only that few uncompleted tasks per workshop. More specialised tasks as well as construcions are only designated after the previous ones are completed.
Getting the hauling tasks done is a bit of a hassle, as I have to adjust my block production for it.
With this little idlers, my lack of party-able rooms, and my fairly large meeting area my dwarves hardly care about eachother, and portion of them being killed is relativelly safe. For the fortress as a whole, that is...
Strangly the dwarves dont seem to mind being slaved to death with merciless efficiency. They are usualy quite contect/happy/estatic when nothing particularly miserable happened to them. Guess they must realy like all the high-value dining rooms, quarters and other fancy stuff.
ps. The building material thing is pretty clever, I think ill try that in my current fort.