Dorfs are generally close to delirium due to alcohol intake
Farming: If it's any consolation, you're not the only one who's made the assumption that creating a farm plot will also cause it to be used. Some hindsight logic shows why you need to: There are several kinds of seeds, so you need to select what to plant. Also, planting selection is per season, so you'll need to make four selections per plot (or use the "all seasons" selection, which I think is vanilla, but might be DFHack). Illogically, underground crops are available only during certain seasons, while overground crops can be planted all seasons (given that the biome permits them at all).
The reason your militia isn't using helmets is probably because you haven't selected "replace clothing". Clothing and armor exist as "shaped" and unshaped items, and the usage of a "shaped" item blocks the usage of other items according to some rules (probably that nothing can be worn on top of shaped stuff). Caps are "shaped" and block the usage of helmets. Check the wiki page on "armor" to find out what goes where.
I assume you order the dorfs to kill using 's'quad-'a'(first team)-'k'ill and then select the target? One mistake is to fail to complete the order, in particular "all in a box", by pressing enter an "extra" time so you actually abort the order (happens to me from time to time). Also, if you order them to kill something and they think they can't reach it, they'll sneak off for training instead, without any notice. When checking the unit list you'll see something about ordered to kill unreachable target.
Water isn't drunk by dorfs normally, but when wounded to hospitalization they ONLY drink water, and will die of dehydration if they don't get it. Also, water is used to clean wounds (preferably clean water that's neither from a murky pool [infection risk] or muddy [lower infection risk, from water of a single tile depth with mud at the bottom, which essentially is all water tiles], although water can be cleaned with a screw pump). "Flowing" water can also power water wheel, be used in water falls for the pleasure of dorfs (yes, it gives pleasant thoughts), clean contaminants (2/7 depth. Deeper (3/7 might be OK as well) and they won't path through it, shallower and it will evaporate), and is essential for obsidianization (which is virtually required to reach the HFS and candy extraction).