Yes the divide scanned images generally works well but it is dependent on how well you spaced them apart on the original scanned page.
Try using File >> Save As
Elements normally appends a different file name with the word edit and copy number.
I don’t think the tiff options are sticky.
You might also try File>Process Multiple Files for saving files opened in the photoshop elements editor workspace.
In case you have photoshop cs-cc, there is Automate>Crop and Straighten Photos, which does what Divide Scanned Photos in elements does.