Note that lens shaped ellipse drawn with the ‘line’, hat’s the Fresnel zone.  Basically you’d really like that entire zone to be clear, and more than half of it is occluded in your case.  On top of that the line is drawn assuming antenna height of 12 meters at each end, and that’s probably not right.  Note that the size of the Fresnel zone varies with wavelength.

Beyond that lots of things can affect signals.  Buildings, trees (especially trees with wet foliage), you name it.  

That said I bet if you put your antenna up another 60 feet things would improve.