My default export is weld body part seams , and include body part names in polygon groups

you can check your obj file by opening it in wordpad or other text editor , and looking for lines starting with g  thats the group name usemtl is the material (surface) name.

It sounds like you may need to log a bug report with smith micro.

That option you have greyed out  is greyed out in poser 7 as well.

you could try export as lwo from Poser. I am not sure what you will get in Lightwave but it might be worth a try.