Deleting songs from iTunes

I have been auditing my iTunes library on my iMac. As I go through each artist, I delete the duplicate songs and also old songs from another era that I no longer want. I am almost half-way through my library of 10,600 songs, and I have deleted almost 2,000 songs. Today I noticed, under "recently added", that the songs are returning to my library! Why? What I do, is right-click the song, click "remove from Library", which brings another pop-up with "Keep File" or "Move to Trash". So I move to trash and then I go and empty my trash folder.

What a huge waste of so many hours! How do I permanently delete the song from my library, never to return? I realize if I purchased it through the iTunes store that it will sit in my account under "purchased" - but how do I get the songs to NOT repopulate my library.....especially all the duplicates. The "find duplicates" mode is useless for a number of reasons that I won't get into. Can someone help?

And, under "Recently Added", the entire album that the songs were deleted from displays......including the songs I wanted to keep! So once I resolve this issue, rather than "audit" my way one-by-one

through the "Recently Added" songs all over again, is there an easy way to display ONLY the songs I've deleted in the past 3 months and then RE-delete them in bulk?