This is an issue with older versions of XPlane2Blender. Be sure to uncheck "Relative Paths" when choosing the texture file. XPlane2Blender was only capable to resolve absolute file paths back then.
You can override the weight of each object, material or bone. The heavier it is, the farer to the end of the OBJ-file it drops. Glass objects however should be within theire own OBJ-file and marked as "glass" in Plane-Maker.
Simply said, don't do that. It is deprecated.
You can attach any attribute to any object (including lights and bones and also materials) within Blender under X-Plane > Custom Attributes. This will save you from writing those into the exported obj file every time.
You have to choose your textures from within the X-Plane layer settings under Scene > XPlane. Textures assigned to materials are not taken into account. Also be sure to UV-unwrap your objects. Generated UV-coordinates are not exported.
Create an armature with a single bone, then edit the bones position to match the axis. Then parent the object to the bone (not the armature), animate the bone in pose mode and do not forgett to give it a dataref and your object will be rotated along the bones axis.
Planemaker shows all animations, no matter if the dataref exists or not. This is a good way of testing if an animation looks right or got exported at all. However choosing the correct dataref is another thing.
Usage: select the objects with the wrong manipulator type and then run the script within blender's text-editor.
In the Material tab, set the diffuse intensity of the material to 1.0 and the diffuse color to a full white. For X-Plane the diffuse color will be multiplied with the intesity and the resulting diffuse color will be multiplied with the texture color.
Example: a red diffuse color of R = 1.0, G = 0.0, B = 0.0 with an intensity of 0.8 will result in a X-Plane material color of R = 0.8, G = 0.0 and B = 0.0. A fully white pixel in the texture will then appear in exactly this color.
This behaviour is however usefull to create colored variations of objects using the same texture.
Also check that the "Emit" value under "Shading" is set to 0.0 to not make the object "glow" in X-Plane.
Note to Cycles: If you're using Cycles to bake the textures, don't forget to switch back to "Blender Render" and assign non-cycles materials to all the objects.