If i zoom in just slightly ill see them but when im zoomed out completely they disappear.
That's not an error and the scenery has been designed like this. Like any good scenery should be, it's optimized with multiple LODs to save fps, so they will disappear if you zoom out entirely. We designed the scenery to be always entirely visible with zoom settings from at least 0.50 ( 0.70 is universally considered the most realistic setting ) so, anything wider than that might not display in all places.
Not sure if this is related but, when approaching from a distance, i find it hard to locate the runway because it seems really blurry and blending in with the rest of the taxiways
This is not a problem of the scenery, of course, but it's a problem of your video settings. You are not using Anisotropic filtering, which will result in blurred textures for any airport that uses a fully custom textured runway (like any good payware scenery should do...)
Use the video card settings to set Anisotropic filtering at 16x.