Good list. I'd add a 6th: the "Discourage search engines from indexing this site" box under Settings → Reading. It often stays ticked after a staging launch and adds noindex to every page. Small note on #4: multiple H1s aren't a problem on their own for Google; a clear heading structure matters more.
I went from zero coding background to delivering 25+ production client websites across WordPress, Wix/Wix Studio and Shopify over few years.
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