export trueSpace objects using the Kilometer Scale!
then it'll be 1 trueSpace unit = 1 DarkBasic Unit
i'm not sure about the box around the object, as i've never had that myself sound odd (please be sure your exporting as DirectX NOT 3DS)
Collision for models is based upon scale in DB/Pro so if your model is sized right then its boundries will be the collision box (remember not to scale in DB as the collision box doesn't scale - not sure why!)
however you can always use the set collision box for the object and make your own collision boundries!
Anata aru kowagaru no watashi!