I have been thinking about your situation, and it seems if you really are showing the file size you indicate, the file is probably corrupted.
It would be good if you could disconnect it from the download managers, but if you can't you might be able to use File Assassin from Malwarebytes to remove it. If you already have Malwarebytes installed, it is included there.
If that doesn't work, I have another way, using the command prompt, to set it to delete during a reboot. Let us know how it goes.