Is there any way to delete everything in Marketo and then go back to the Old List and clean it up and then re-upload?
It's ok to send an email once in the US, but with all of the changes in Canada and elsewhere, I'd be reluctant to do that without permission.
From the way you described it, I am a bit unsure if you mean the list has Spam Traps, Old Emails, or you just transposed Unsubscribed=TRUE for FALSE. Let us know.