Your existing antenna is our ClearStream 2 which is NOT omnidirectional. Its reception pattern is on page 3 of the data sheet located here:
http://www.antennasdirect.com/cmss_f...%2BVHF-TDS.pdf
Your antenna is also assembled incorrectly. The base and loop element are 180° out from each other. That hole in the base is there to pass the cable through to the connector so as to not force the cable into a tight-radius bend.
Off-axis reception using a directional antenna is going to be pot luck. While the signal power might be adequate, there's often a problem with multi-path caused by the antenna picking up reflected signals that cancel or distort the off-axis primary signals. It's pretty much impossible to predict what might happen.
Are you open to a rotor or, if not, to multiple tuners to avoid antenna combining conflicts or problems? Simply combining antennas faced in different directions is another pot luck situation.