If you have a non-repeating mapping, you still need to identify what field in your form (non-repeating) you want to use for the SharePoint List Item Id.
In your current sample form, I don't see a field in the data source that makes sense for this, so I'd add a new field. Then use the full XPath to the field.
I've done this to your sample and am attaching it.
For some reason, you keep seeming to want to use a group (a folder icon in the main data source task pane) for the id -- but we need an actual field. If you don't have a field already to use for this purpose, you can create one. Again, it doesn't have to show on the form.
The purpose of the ID field is so that if you re-open the saved, filled out XML, and you modify the item that has already been submitted to your SharePoint List, and you re-submit, instead of having a new item created, the original item is updated. This may or may not be what you want to have happen, but like most qRules commands, SubmitToSharePointList has been engineered to try to provide the form designer with as much flexibility as possible. The intent of qRules is to give you a collection of tools that you can use in tandem to replace the need for custom code in your forms.