[Flint Ridge]

Ok, looks like you will get an answer from a non-pro to ponder. Given that you want FOX a very weak UHF station the following is suggested. Forget the idea of the existing setup. Go with a roof mounted tripod. Study piece of 8' or so 1 3/8" chainlink fence toprail.

DB8e from Antenna Direct for the UHF portion, which is channel 15 and above pointed directly at Fox at 70 degrees. You might be able to pull it in with a 91XG, but the advantage goes to the DB8e and I presume you want to get it right the first time. (UPDATE - looking at my past calculations the DB8e only has about 1 db advantage on that channel. So, given the smaller size of the 91XG and ease of handling you could easily do that instead.)

For the HiVHF I would go with an Antenna Craft Y10-7-13 4' below the DB8e. Pointed at 81 degrees for your weaker HiVHF stations. (I'm presuming you do not need LoVHF channel 6. If you do, please advise as that changes everything) (Double UPDATE - Antennacraft Yagi HD Antenna Y5-7-13 is cheaper and you have plenty of signal I think for the smaller and cheaper version to work, would be a nice setup overall with the 91XG)

Connect with new RG6 coax and compression fittings and waterproofed outdoor connections (coax seal tape). How many tv's and tuners are you hooking up?

Amp suggestion would be to try an RCA TVPRAMP1R Antenna Pre-Amplifier. Set in combined setting, click to verify, FM filter on and connect UHF to UHF side and VHF to VHF side.

That is what I would try. Actually you are lucky with your signals being arranged the way they are, this makes thing much easier. Best of luck, others will chime in as well.