Help fixing minor SEO issues with site

Been running our site [thesantegroupinc.com] through various SEO analyzer sites and have a few questions about how to fix some issues (if these are indeed REAL seo issues in your opinion) :

  1. “Fix errors regarding the language markup of your page”
    “One or more of the specified languages are not ISO standard (en, en-us, de, etc.)”
    – I have {html lang=“en”} in the custom code section, is there something else I should do?

  2. “Remove the empty bold and strong tags from this page.”
    – I get what this means, but I haven’t found a good way to go through and find what isn’t being used?

  3. I always thought that robots.txt and a sitemap were done automatically by Webflow, apparently not?