Hello,
I checked and now I do see the xstore-customer folder with all original files so thank you for making a backup. Most of the modifications were located in functions.php and some other template files that modified the admin panel like adding numbering to the pdf invoices, extra product fields etc. I’ll restore these back into the child theme after the qty issue is fixed. The old versions of XStore for some reason never worked with the Child Theme but the latest version does. I did noticed some styles are not overriding properly under the child theme but I’ll take care of it. For the moment please fix the qty issue from the product listing and the product slider on the homepage.