and thanks for the images and details. The task appears clear now but I must admit that it won’t be easy to come up with satisfying results.
Here is an analysis of the orientation distribution of your sample image:
The plot starts with the horizontal orientation and the orientation angle proceeds counter-clockwise.
It is evident, that the vertical structures in your image are at least as dominant as the more or less horizontal ones that you are interested in. Any analysis will thus be disturbed by the vertical structures. Consequently, you may try to suppress the vertically oriented structures first.
Finally, it would be highly desirable to see images with considerably higher spatial resolution.
HTH a bit