Daas Yochid: #1 I haven’t seen that quote in any of Rav Belsky’s statements on the issue, but it would only be relevant to his opinion that minei gavli applies even to a visible worm that grew larger in the fish. In any event look up the Chavos Daas and you will see from his examples of a bria (eg. the shilia of a donkey) that it would CERTAINLY apply in our case.
#2 Based on the size of the krill ingesting the worms and the size of the worms when the enter the salmon, I think it is safe to assume that the anisakis larva are minuscule. So did Rav Fisher, Rav S. Z. Auerbach etc.
#3 Look up the Michtav MeEliahu, where he uses this sevara to permit killing lice on Shabbos, which is “chayav” for paroshim according to the Gemara.
#4 I am disappointed to see that you too are stooping to partial quotes out of context.
I am in EY, don’t know where you are.