Hello,
1) Try to register theme now.
2) Don’t see issue with this.
3) Edit that page and disable the breadcrumbs in the page settings http://prntscr.com/vlnl94
4) If you switch to the default theme and test site and then back to XStore you probably just need to re-add widgets to correct widget areas, that’s all. You won’t lose any other data.
Regards