Hi Susan, I am not sure why you are not seeing Lead Owner filters as options for your smart lists. There are several 'owner' field filters available (I've screen-shotted a few, below).
Further, when you uploaded the leads from SFDC into a static list in Marketo, did your import file contain the email address of the lead records? Marketo de-duplicates based on unique email addresses available, so if you imported lead info including email address it should not have duplicated the records. If you uploaded a file with partial information, such as just first and last name it very well could have created duplicate, and incomplete, versions of lead records already in your SFDC.
Can you provide any more details about exactly what you did that resulted in this scenario?