Thank you for the credentials, first please clarify what is the issue, what was deleted. I'd checked your home page and all your content was pretty much there (see screenshot below).
Since you've just updated your theme, please clear all caches (plugin, server-side, CDN, and browser's cache) so that the code from the latest release is always in use. This will help you to avoid any potential errors.
Regarding your questions on the secure note:
1) We love to do that for you, but we need FTP credentials.
2) I think you're looking at X > Theme Options > Integrity that is not the right place. Template Manager is under X > Templates.
3) Its there (https://image.prntscr.com/image/lDBI0a9YTfa1qz4pJHYMGQ.png), please clarify.
4) Navigate to X > Validation > Extensions, and install the extension that you need.
5) That is the Breadcrumbs let us know how do you want the Breadcrumbs to look like, you can turn that off if you want under Theme Options > Header > Breadcrumbs.
To make your section fullwidth, use a Blank - No Container, Header | Footer page template on your page, and then turn off the ROW's Inner Container option, then set your image width to 100%
6) Under Page Settings > Meta Settings you can set Background-Image per page.
7) Yup, your General Settings are all good.
8) I don't see any customization you did on the child theme, so it's not going to harm your site, it's all good too.
9) I don't know what plugin you're going to use, if there is an extension that you want to use, please refer to #4
Hope that helps,