Daas Yochid: #1 the Chavos Daas is explaining the words in Shulchan Aruch 81:4 that the shilia of a donkey is MUTTAR, not assur miD’Rabannan. He also explicitly differentiates between the halacha of hayotzei min hatamei which does NOT apply to a bria and eiver min hachai which does. If you want to invent a new halacha of “the status of its host” you need to bring a source.
I’m not sure what you want from the previous post. The Gemara that basis the heter of flesh-worms on minei gavli is describing a perception that they originated in the flesh, according to Rav Dessler this is not necessarily dependant on the reality. I am not certain according to Rav Dessler if his rule that Chazal knew the true reason even when they described a non-scientific explanation applies to the Rishonim as well, it would seem not. In our case it would appear that the the Rishonim took minei gavli to literally refer to spontaneous generation. Therefore to answer your question “Do you think the anisakis worm is the worm which the Shulchan Aruch discusses, or is the heter based on a sevoro not reflecting the case of the S.A., but yet a compelling sevoro?” I would answer that it is certainly the same worm, but the true reason to be matir MAY NOT be the one Shulchan Aruch refers to.