It looks like you have plenty of signal to work with so the antenna you chose is fine. Your aim point is good, I don't expect that antenna to be very critical about aiming. In fact it will likely allow reception of strong stations behind it's aim point.
Use RG-6U cable. [I'll retract my other comments and defer to John Candle's Posts re. connectors and water proofing]
When you scan for channels be sure that the set is set to antenna mode not cable.
Stay safe on the ladder.
