mms601: Simply qouating R’ Eliyshiv etc.
quoting someone who quotes someone else gives you two opportunities to quote out of context, which you did spectacularly well. Let’s stop for a minute and think, if the Rishonim would clearly state nignuz means until after moshiach comes, is there even a safek that no matter how many proofs we would bring about a specific animal being the chilozon, it would definitely NOT be the true one? Of course not! And if someone would say in such a case that being we know for sure that it is the chiozon obviously we are mechuyiv to wear it, such a person may correctly be deemed a heretic for he disregards Chazal according to the Reshonim, and places his own opinion above them.
Now does the Yeshuas Malko state that it is possible that someone will be able to know for sure that a specific animal is the chilozon? Yes he does. If the Yeshuos Malko believed that niguz means literally would someone be able to find it? Of course not! Obviously the Yeshuas Malko did NOT understand it to meant literally.
In regards to the ridiculous statement of שוויה אנפשיה חתיכה דאיסורא. Before making up halachos it is a good idea to learn the relevant material first. שוויה אנפשיה חתיכה דאיסורא is not said if one made a mistake, see Y”D 242: and the achronim there.
Furthermore, if one changes his mind and decides that it IS the correct one, that means that he is mechuyav min HaTorah to wear it, שוויה אנפשיה חתיכה דאיסורא CANNOT uproot a deoraisa! (Think about that, can I make a שוויה אנפשיה חתיכה דאיסורא against Tefilin and not be mechuyiv to wear them?!)