I don't know how you came to those numbers (6 and 24), but according to your settings, autosave should save 40 images at 20 min intervals befor it starts overwriting old files. It doesn't care if you rendering single images, batches or animations.
As for the second question, part of stats can be saved with render stamp. There should be ability to save it to xml file, but i don't know much about it.