Can I find a private key for a known encrypted file?

Let’s say I create a 100KB file only containing 1234567890, that is, a known value. This file would be sitting on several folders as bait.

Once a Rasomware hits the folder and encrypts this file (considering all other forms of anti-rasomware protection failed), could I generate which is the private key that would decrypt that file, and all other files, by knowing the previous file contents?

Does also having the Public Key captured in memory help?

Does having a large known file help?

I know this goes against the asymmetrical key theory, but usually there’s a difference between cryptography theory and practice, like hashes should be unique for every entry, but in practice there’s always the possibility of collisions.