Another way is to use the RedirectMatch directive.
RedirectMatch temp "^/folder\
As single line
RedirectMatch temp "^/folder(?!/subfolder|/exclude-file1\.html$|/exclude-file2\.html$|/exclude-dir)(.*)$" "/folder/...
<link rel="stylesheet" href="http://www.example.com/amazon/styles-site.css" type="text/css" />
The problem will be that you are linking to an HTTP (non-encrypted) resource from an HTTPS (encrypted) page. When viewing the HTTPS page (possibly after an initial redirect) then the browser will block any requests for HTTP ...
In GSC, add the shop subdomain as a profile and make sure there is a profile for the main domain too. Give the new profile(s) a day or two to get situated.
If you haven't already, pick either www or non-www for your main site and make sure the URLs with the one redirect to the URLs of the other. Here's how to do with Apache for instance: https://www....
There are other ways - repurpose your content into one. Your question is more related to your traffic decreasing. First, you need to track your keywords from your old pages. What keywords you are ranking, try to identify the keywords gap between the old pages and new pages - Does the content still serve the same purpose to capture the same keywords/intent ...