Hi Patrick,
In short, for both the widget needs to be changed. Please create issues for each on the GitHub repository:
https://github.com/Itvisors/mendix-DataTables
Currently, the sort is defaulted to the first sortable column. But when statesaving is enabled, that will overrule the default. So I doubt wether adding descending sort to the configuration will help you as the user can change it.
The progress bar can be added. No problem there.