Yes, as Fleeting Frames indicated, turning off job cancellation spam reports (as was done in the fortress referenced) hits you hard when suddenly nothing is happening.
I definitely would spend my effort on getting the fortress back on track rather than archery training and do the quick fix for the weres, which is to brick them in (the best case is to have them do the wall building themselves, but there's a significant risk they won't stand on the desired side of the wall). When things are back on track, were elimination could be given a higher priority.
If most of your fortress pop has been eliminated, it presumably also means that most of your job assignments have been eliminated as well, so you'd need to reassign jobs to the remaining dorfs, and remove assignments to jobs that aren't needed immediately.
Corpse hauling is likely to be very important, so the corpses are out of the way when new migrants come, but it might be overshadowed by the need for coffins to bury them in, and slabs to put their souls to rest if you can't produce coffins fast enough.
To trouble shoot, you can either make the save available to the forum (using DFFD
http://dffd.bay12games.com/, for instance) for others to help you, or you can try to identify the issues yourself. Forgetting to remove civ alert burrows is one common problem (doesn't sound like it's the cause in your case, though), cancellation spam where the same job is taken and immediately dropped another (often caused by civ alerts blocking dorfs from actually performing jobs outside the burrow, but not to take the jobs). Locked doors or other path blocking measures will also stop jobs at the inaccessible location (without any cancellation spam: the job are correctly filtered away before they're assigned).
Thus, I'd check that the correct jobs are assigned on the remaining dorfs, look for cancellation messages, and look for other indications of what jobs they are taking and which ones they are not. Corpse hauling, for instance, will stop once the corpse (NOT refuse!) stockpile is full, which can easily happen after a massacre. Workshop (re)building typically requires one of the jobs performed in the workshop (check the wiki if you're uncertain), and some building tasks requires an architect job to collect the pieces followed by an assembly job using the appropriate job skill.