Anyone heard of them being DDOS'd? This certainly sounds like ongoing DDOS and protections kicking in (assuming that by "verify my account" you mean "having to solve a captcha").
As an instance owner I can say lemmy.world is a bit of a troublemaker as it will constantly halt and resume federation activities in a very bursty way and cause momentary spikes in resource usage. I have now upgraded the instance enough that it's not really a problem, just an annoying observation.
Having said that - feel free to test run my instance! The only problem I am currently aware of - gmail outright refuses to accept email from it, so verification is impossible. Thanks, Google! Have not had any reports about other providers, though!
I noticed Jerboa saying something about my account being verified on lemmy.world in between 502s and other network errors. I've never seen that before, but looks like it's not exclusive to you.
I am also in nine other instances. But I have some communities on this instance that I don't know how to move into other instances in case this one goes kaput.