Yes it has been said that V-Ray Next will support MaterialIDs in GPU mode.

I like use a Mix Operator tex in the Diffuse slot with the Occlusion map on top set to Multiply, then of course you put the albedo map in the bottom slot.

You can also try exporting your DXF file as an older AutoCad version. I export all the way back to AutoCAD R2.5. It's not perfect, but it is much better. Adding extra points to the curves before you export the DXF will also tend to help

You can also set the Material ID color in the material options. Sometimes this field is set to black.

which driver version and which GPU?

Make sure you ticked the 'Spherical' option. So that image wraps around and you won't see plain ground.
And i think your only option is rotating (i might be wrong). But making changes other than rotating doesn't make sense, because it'll shift the horizon etc.

I think the question has more to do with the modeling software. In Max - the sun is just another lamp in the model that you can manipulate. In Sketchup - the sun is not present in the model, and the only way to adjust is are by the "shadows" settings.

Hi there! Change the time settings in the Shadows panel. Usually setting the correct time zone, will get you correct day light.

In general you must rectify the vertical geometry on the original Photo!