Why won’t a military Dwarf work

I would suggest using a manager noble and the management screen (j, m) where you can queue up tasks. I find it useful to do thinks like:

• Queue 15 barrel
• Queue 15 brew drinks

And jobs that are managed are automatically re-assigned if they fail for any reason including lack of resources. So in this case the brew drinks would be re-assigned until the barrels are available to complete them.

Note that these tasks will process in parallel.

Moose Men and Women, like their Moose kith, are dangerous due to their size, but won't go out of their way to get your dwarves, either. (Unlike the evil, evil Honey Badger)

This is a very literal case of "they're just as afraid of your dwarves as your dwarves are of them".

However, it sounds like your dwarves may have accidentally cornered a Moose Man or several, and, like all cornered creatures, will defend itself vociferously. Since you have several dead dwarves on hand, it's likely that they simply wandered too close for their own good.