sam2-your first quote is a misconception. Once you accept that the milk from that cow that is milked is kosher (based on rov) it does not revert to a safek ( or treife)afterwards-hence, once the milk that is milked from one cow is kosher, it is totally irrelevant whether afterwards the milk is mixed with hundreds of thousands of gallons of other milk, amongst which there might be treife’s.
I have no idea what your quotes of Rav Elyahsiv and others mean. where do you have “javsh bejavesh” here? (milk is lach by definition)
On the second quote- obviously the Shach disagrees with you and so to most others. Are you telling me that if you murder a person that has a needle in his lungs and will live twenty more years, you are not ‘chayiv”? Preposterous !
And yes-if you murder someone with terminal cancer -it may come under the heading of “Hahoreg es hatreife” and is pottur.