Aha, looking good!
I inlined as many static meshes as I could for d3dm1: https://drive.google.com/open?id=0BwE6dxM0O2PsU20xdTZYSHF5bU0 Please give it a try.
I was also thinking maybe it makes sense to load .cm as collision mesh and give it per polygon collisions in UE4 or if it makes more sense to load brushes from .map and turn them into collision primitives. What do you think ? (or have an option to do either of them - for PC collision hull should be fine, but for mobile collision primitives would be better maybe?)
Btw, why are some textures mission on the second pic? (that curves patch on the floor most likely was used as a decal)