Hi Pat,
There are definitely parts of this you could automate.
Since it appears that the layout of the project is somewhat similar for your live recordings you can save a template as you are doing. Additionally within the template you can save several Mix recall scenes for the different mixes you want. Take a look at
Mix Recall for more info. You can save individual scenes for "full" "No BG Vox " "No lead vox" mixes within the template itself so you need to do this setup only once. Then you can simply bounce all the scenes in one go to get all your mixes. From your description it appears that each scene just has different track mute/solo states so it should be pretty easy to set up the scenes.
With regard to splitting the project into different songs I think what you are doing is OK. From the master project just save multiple versions to individual songs, and then delete the unwanted sections.
Overall I think this approach will avoid the need to do submixes first to clips and then a second export of the clips. Also if you save the scenes in your template this will need to be done only once.
Hope this helps speed up your process...