on the silk question, i haven't tried making it grow like you've suggested, but have a pretty easy workaround, using the silkworms from genesis as a base. you could do this with phantom spiders, too, or any other vermin-sized silk-producers you create
give them the [VERMIN_SOIL_COLONY] tag and make sure to *not* add [ARTIFICIAL_HIVEABLE] unless you want them to only produce one silk every six months or so. also, ensure that they've got the tag [COLONY_EXTERNAL] too, so they'll spawn around their home (like bees) and start spitting silk everywhere. if you also give them the [PET] tag, you can potentially have access to individuals at embark or via trade, and keeping one in a cage somewhere safe will have others spawn around it, dropping silk to harvest in a nice indoors location
i'd also done a variety of other silk-producing critters (like a spider that totally replaces cats in my fortresses) but, they don't seem to actually shoot their webs. you just occasionally find batches of them on the map. however, war-trained gcs *do* leave quite a harvest behind if you give 'em a groundhog or something to attack
another modder had included a type of large spider that bleeds silk when hurt. it's a rather interesting way to ensure you get more than just the 'starter' silk spawns when you first enter a map