They list a service for each address, so maybe you could block all the non-Route 53 IP addresses. Although that assumes they aren’t using the Route 53 IPs or unlisted IPs for scraping (the page warns it’s not a comprehensive list).

Regardless, it sucks that you have to deal with this. The fact that you’re a customer makes it all the more absurd.

If you only block new inbound requests, it shouldn't impact your route 53 or DNS-01 usage.