1/ Update the theme and Core to latest versions. https://xstore.helpscoutdocs.com/article/63-theme-update https://xstore.helpscoutdocs.com/article/37-plugins-update
2/ Provide temporary wp-admin access via the Private Content area here.
Create an account via Dashboard (Users > Add new) with administrator role http://prntscr.com/s3rc9m > provide us with username and password via the Private Content area http://prntscr.com/s5mao7 You can use any email for it.
3/ What exactly emails are received by customer? Please describe the situation in more detail with screenshots.
You can use Lightshot screenshot or Gyazo tool to make screenshot and share the link here.
One standard license is valid only for 1 project. Running multiple projects on a single license is a copyright violation.