#1 Again I repeat, see the Chavos Daas.
#2 From what I have seen the worms entering the flesh of salmon are approximately 1-2mm, borderline nireh l’einaim. When they enter the krill 2 developmental stages earlier they are clearly much smaller then that. The only Posek I have seen concerned about the size at this stage is Rav Vaye, and he explicitly writes that he is NOT basing his concern on specific information, just on lack of trust in the scientists to define nireh l’einaim.
#3 I’m not sure what you don’t understand. Both Rav Kuber’s heter for anisakis as well as the ossrim are based on the literal understanding of the words minei gavli in the Gemara as spontaneous generation. They primarily differ on whether we concern ourselves with observations that seem to point to alternative sources for the worms. According to Rav Dessler we need not understand the Gemara is basing it’s heter on spontaneous generation at all and we can follow the psak of the Gemara and Shulchan Aruch to permit worms found in the flesh of fish even if they certainly originated outside the fish.
#4 I wrote that this derech may SEEM radical, but in truth it is logically compelling and also accepted by many Gedolim.