@slav-arcadechain I think I figured out part of the puzzle:
AWS has a second admin panel to set the name servers when the domain was registered with AWS. These servers seem independent of the NS records listed in the DNS panel.
Go to the Route 53 Dashboard → Domain Registration (NOT “DNS management”) → Select domain → Add or edit name servers
The listed servers were still pointing to AWS despite the ns records I added in the DNS management section. After I updated this list, the website was back up. The SSL tool still won’t verify the DNS for the certificate but it’s only been a day since I made the change. It’s progress, though.
Maybe this helps if you decide to try moving your DNS back to Netlify. Hopefully the certificate works after some propagation?
Tony