From talking with a few local folks my take away is the numbers published is the very highest amount you could get and isnt always what you will get. 

TN offer OTC, it's extremely benefit to locals that knows the area well.

Is this a commonly successful approach given the local real estate and rental market dynamics?

I own and operate a local firm here in Green Bay.

Local investor and investment focused mortgage broker in Middletown.

I am an agent and investor in the area and I'd be happy to connect and chat more about strategies and the local market. 

Nobody seems to have a problem with a plumber or appliance repair guy charging $100, sometimes $200 to give them an estimate on a job.

Given that it's an ADU and you are an owner occupant I would courteously terminate the lease (the how on this is going to depend on your local laws and your lease) and get a new tenant ASAP.

If they treat you like the existing owner:The tenants would pay between 1st and 5th give or take (depending on local laws about when rent’s really “due”.

Check with some of the local REIAs to see if there are any interested buyers, have the host blast out an email to all members.