I personally would break the model up into walls, ceilings, floors, to get a better collision on it.
That would also reduce the number of poly per individual piece in the x file. then you export them from there location, then insert them into the editor all from the same snap location, aligning everything perfect with no adjustments needed.
I would try and reduce the number of multi texture to 6 or less. I would probably combine as many as I could based on wall, ceiling and floors and remap the individual pieces, thus being able to use the entity_basic shader.
Same thing with the castle.
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