A second antenna is an option... Combining the signals from two antennas can be a technically challenging task though.
As John has already mentioned, the Terk antenna may not be ideal for you; The amplifier may be overloaded by the strong local signals. Your report lists ten transmitters 1.4 miles from you.
I suggest two antennas:
The first, a 4 bay panel style such as a DB-4 or CM4221. Aimed at 158° per your compass, you should easily receive enough signal to drive a 4-way splitter with no amplifier needed. This antenna would not need to be mounted at the top of the mast even.
The second antenna I suggest would be a combination UHF/high-VHF such as a Winegard HD7697 aimed at 230° (compass). If you include a high input preamplifier such as a Winegard HDP269, you have a very good opportunity to see KXMN-LD, a MyNetwork affiliate.
Rather than trying to combine the signals from the separate sources, I would suggest using separate runs of coax and A/B switches. Or consider
http://forum.tvfool.com/showthread.php?t=820
(Looks like I typed slow - TG types faster than me...
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