think you need to basic use the terrain only that was converted over and skip the items. try to pick new item and that are in the game already or take the 3d files use something to resize them to work in DF: Xtreme game. sorry don't know all the details.
but then again your getting into copy right area here import items from BF2 into another game.
object are size to work for said game, i think you need to resize the image files to work in DFX.
here a Mod site link:
http://www.dfarena.com/
they maybe able to help you ether get them 3di file to work in DFX as a mod
Dfarena forum mod>
"3D Editing & Terrain Building"