You are lucky that the FM-6 has about 4.5 dBi Gain on Ch2-6 and about 5.7-6 dBi on Ch7-13....where it is Bi-Directional [Equal towards Front and Back]....although with Excessive SWR which could be degrading TV Reception.
However, in UHF Band Gain is all over the place, with narrow beamwidth peaks as high as 3-4 dBi towards SOME [Odd-ball] Directions and mostly 0 dBi or Negative Gain in most other Directions....all of which varies by Frequency....but I was surprised to see that SWR was in ballpark of 3-4, which isn't all THAT Bad. Since MOST of your TV Channels are in UHF Band, FM-6 may be preventing reception of SOME of them.....esp. PBS.
By clicking on your name, I can see that you have similar posts in the RAYLEIGH, NC Thread [there is NO WAY I/we can monitor ALL city threads], but we STILL don't know WHERE you are located relative to Towers. You should enter your location into www.tvfool.com
and copy/paste the Results Web Address [URL at top of Web Browser] so that we all know what you SHOULD be able to receive and if you let us know what you DO and do NOT receive, then we can provide advice on what more your are likely to be able to receive with a REAL UHF TV Antenna. [BTW: I think that your FOX is on WRAZ, Real Ch49, Virtual 50.x., which has currently gone MISSING from TVFool.]
You should also enter location into www.fmfool.com to see relative signal strengths and direction of FM Stations. Typically if you have nearby Line-Of-Sight (LOS) TV Stations [which you obvious do], then there likely ALSO very strong FM Stations nearby that COULD be causing problems to Ch7-13, for which we MIGHT be able to help you improve reception.
PS: The Magnavox T-26 connected to FM-6 is a very broad band [ALL CATV Freqs...but it's an INDOOR Model] 300-ohm Antenna to 75-ohm Coax "Balun". I highly recommend replacing it with a new OUTDOOR model [Channel Master and Philips have lowest Loss], which has DC interconnection between Antenna Elements and Coax Shield to ensure that Static Electricity on Antenna Elements is drained off to Safety Ground via Coax "GROUND BLOCK" that is SUPPOSED to be used at entry point to house....a MANDATORY requirement of NEC Code that also helps to redirect most of the energy of a Lightning Strike to an appropriate Safety Ground.