Use a fixed number of digits for exporting with custom name and sequence, potentially as a parameter with a default value of 3 digits that the user can modify.
I’ll put that on the list for a future release.
Export in the (chronological) order in which the images are being displayed in Raw Power.
This is a bug – it should respect the sort order. I’ll put that on the bug list.
When exporting files, set the file creation date to the original image capture date.
I checked Aperture, Photos, and Lightroom. None of them set the file creation date to the original image capture date (all preserve the EXIF capture date, as does RAW Power). In general, I’m hesitant to mess with file creation dates. If the other two issues are resolved, I believe your situation would be okay, since the images would come in the right order.