OCGD, I received the following reply from Live Writer Technical Support regarding our split post problem. I use Blogger too:
Thank you for writing back to Windows Live Writer Technical Support. I understand that the split post feature is grayed out when you create a bog post for your Blogger or Blogspot account using Windows Live Writer. I know how important it is for you to have this addressed.
Windows Live Writer does not currently offer the split post feature on Blogger accounts. However, I will submit this item to our product team as a feature request.
I cannot give you specific dates on when you will see changes, but we are working hard to update Windows Live Writer and better serve your needs.
We appreciate your continued support as we strive to provide you with the highest quality service available. Thank you for using Windows Live Writer.