I don’t have a property license posted in my apartment …

I would start by reviewing "Tenant's Rights and Responsibilities" on the Minnesota Attorney General's website.  Good luck ... overpriced, crappy rental property is a problem in Duluth.

A great free resource is Home Line. They can provide free legal help with your issues.

Duluth Construction Services & Inspections

Scroll down to the Life Safety Office. You will find the information you are looking for.

The rental license does not have to be displayed, only the contact info of the landlord or manager, which should be displayed on the outside of the building. However, compliance with that rule is low, and there doesn't seem to be any repercussions for noncompliance, but the police department is currently working to correct the issue (see article). 

Eyewitness News: Duluth Police to begin rental license compliance checks

Any reason you continue to live in a dump with a shitty landlord?  There are plenty of rentals available on Craigslist for around $815 and under.

That being said, if your landlord keeps trying to cut you off when you bring up issues, that's a sign your landlord doesn't have your best interests in mind.  Relator Brok Hansmeyer is a great landlord--one of the best in town and might be able to help you find a quality rental in your price range.

http://www.brokhansmeyer.remax-northcentral.com/

Call the Life Safety office, find out when the building is due for re-inspection and tell them your concerns.  Better yet, send a letter or e-mail.  The license I think is supposed to be posted in a common area.  The landlord contact needs to be visible from outside the building so it's accessible to Emergency Responders.