I did not understand the 1st question. It sounds like you are not importing a single object, but a few objects, or a group. In such case, Corona Scatter will scatter each object separately. The solution would be to attach all objects into a single object. (convert to editable poly and then attach all of them to one object, so that you would end up with a single editable poly)
About the 2nd question - different software may interpret the same object differently. You would probably have to export your object using some other settings, but even then 3ds Max may not be able to "see" it the same way Rhino does (I have no experience with Rhino at all).