I like this idea. Though i feel there may not be a need for another separate skill, milkers or animal caretakers should be able to handle the job. The animal also shouldn't have to be caged if fully tamed, as opposed to trained, and tamed animals should be significantly less dangerous to milk than trained wild animals.
I would argue that Dwarves should absolutely be able to make blowguns, and also make them out of glass. This should be possible for their use in traps, using a leather bag or waterskin with a blow gun to create a deadly version of a bagpipes, set in a trap in the walls or floor, the darts to which can be poisoned. Obviously a pressure plate compresses the bag to launch the darts.
I do feel that blowgun darts should hold a higher quantity of venom than other weapons, not necessarily last longer. I.e. a blowgun dart should be able to deliver 3 to 5 times as much poison/venom as other forms of weapons, but the decay of the toxins over time should be the same (if it's a set units lost/month, then obviously blowgun darts would last longer) washing items with water should remove the contaminant from the item and spread it into the water.
I would even go so far as to beg for a task designation to allow us to designate any item to be coated with any liquid, including plain water. Items already installed as part of furniture should absolutely be possible to target, such as weapons and trap components installed in traps. That's a feature we've been waiting to see for a long time now. Like, 10-15 years. It'll probably be a while yet.
I would also add magma+water powered steam pressure generators for a new type of mechanism that can activate traps, raise/lower bridges, power machinery and of course fire blowguns. Even blowgun siege weapons based off ballista arrows and pipes, but that deserves a separate thread as it's way beyond the initial scope of this suggestion.