hello99:
I am not familiar with the soap making process. If the tarfus is degraded in itself, then we could apply the rules you reference.
However, we can go further than that, since here we are not eating the soap; there is only nesinas taam. Therefore, we can use the rules of n”t lfgam that I referenced which are more meikel.
Now, can you elaborate on the din of nveila sh’eina reuya l’ger? It looks to me like the Mechaber is matir when a rov issur falls into a miut heter and it is pagum lgamri in siif 2.