My 2 cents about the runway:

Open the scenery in overlay editor , locate which file is used fot the rw textures , open this file and check if there is somthing related to LOD , if so , delete it.

THANK YOU!! This did the trick.

 

The relevant files for ground markings and runway textures are:

 

mdpc2014_solowiz-mdpc2014_asphalt.obj

mdpc2014_solowiz-mdpc2014_lines_01.obj

mdpc2014_solowiz-mdpc2014_lines_02.obj

mdpc2014_solowiz-mdpc2014_rwymarks_01.obj

 

All these files contain at the end a line like

 

ATTR_LOD_draped 1560

 

I removed the line completely from the 4 files (but probably one can also change the value), and now the runway and the markings are visible even in low world details distance settings. Here's a screenshot:

 

 

Note that this is "very low" world detail distance, and still I can see the runway markings from high above. Before, everything I could see from this height was a blurry mass. Now, the markings are perfectly visible.

 

There are some more .obj files beginning with mdpc2014_, but for me changing these 4 was enough for a good result.

That are very good news! Thanks for these informations! In the meantime i received some improved files from tropicalsim, but i will try this as well.