1. In the main DataAssist: Create Pages wizard, on the Manage Pages screen I thought there would be an option to specify an After Insert page, but don't see this anywhere. Its easy enough to edit in the code, or the Insert Record Behaviour, but just wondered if I was missing it at this stage? 
For now it seems that we need to edit the code to make those changes, someone from WA can answer if that is a proposed feature. I for one would like to see these pages simply default to the resuts page after insert or update as a quick fix, but being able to specifiy it in the wizard is a great idea.
2. Very much like the Configure Field Settings screen, with the label and validation stuff on the same screen. Again, I thought there would be an option to specify the validation messages in there, but don't see it. (Although again its easy enough to edit the default one in the code.)
Again, same here.. you are doing it the correct way for now, but I agree that it would be nice to see the option to change those messages from within the wizard.
3. After I've finished the Create Pages wizard, is it possible to open it again and edit, for example add more pages, or go back and add / edit fields in the insert / update pages?
Once the wizards are generated you need to edit the behaviours that are created on the pages to make any changes, you can't go back into the wizard afterwards.
However, if you save a design preset for each new page setup, you can delete the created pages, re-run the wizard, chose that preset then make your changes, re-save the design preset and recreate those pages via the wizard quite quickly.
If it is a matter of design changes for the fields (size, type, etc.) then click on the preview window for the page you are defining within the wizard to get a preview in your browser to make sure they are ok before you create the pages.
Hope that helps, and I'm sure someone from WA will chime in with further info. :)
