Just trap them all out. That doesn't require any math.
It *might* be FM and a filter is easy to install. If you're not using an amp, it's much less likely but still possible that FM is interfering with that station. Given that your antenna isn't particularly sensitive to FM (it's probably down -5 to -10 dBd) and you didn't indicate any amp in use, FMI wasn't my first suspect.
There are several interference mechanisms for FM to interfere with VHF channels 7-13, the second order harmonic is the most common. To identify suspects, proceed as follow:
Identify the beginning and end frequencies of the TV channel. KMSP operates on VHF channel 9 occupying 186-192 MHz. Divide those frequencies by 2 which results in your suspect(s) lying between 93 and 96 MHz. You've got over 1.2 million watts of FM radiating from a site about 6 miles away of which several are in the suspect band. In other words, it's probably not a single station (if it's a case of FMI), it's a cumulative effect.
If you have any remaining Radio Shack stores around, call them and see if they might have a 1500024 (15-0024) FM Filter on hand. You'll have to call, do not rely on the website as many stores still have stuff leftover from pre-BK that isn't on the website.