submeshes or geosets, same thing
Ok 1 texture.
Try to open your m2 with 010 editor and m2 template
Go to struct Textures
then struct Texture_texture
and enum E_TEXTUREFLAGS flags
If the flag is 0, Set to 3 and save
If don't work try this :
Open the .obj file
Save as 3DS
Open the 3DS file
Save as .obj file
And use this last .obj file in the objtom2 converter