I agree, WTIU is so strong that it may be receive with no antenna connected to the TV.
A technically viable approach would be to insert a band-stop filter between the antenna and the input of the preamp.
www.tinlee.com offers custom filters, you would need to contact them for pricing. The tinlee CR7D-(Fo) UHF HT would be a potential fit in this situation but I would share your TV Fool report with them. They may have additional ideas for you to consider. You would want the filter to provide relatively consistent attenuation of the CH-14 bandwidth (+/- 1 or 2 dB) if you want to be able to tune the signal after it passes through the filter. You would want to be sure that the filter attenuates at least 30 dB, 50 dB would be ideal IMO. The filter needs to overcome the power in the air plus the gain of the antenna.
I call the filter 'technically viable' because you would need to decide if the cost is acceptable.
With the CH-14 signal reduced in level, you can then use quality consumer grade antenna system parts such those already mentioned. I would install an Antennas Direct CPA-19 preamp to the output of the filter. Avoid long coax runs between the antenna > filter > preamp.