It appears that most of the requests were being made to the ~8 images on the homepage, so I've moved these to an S3 bucket and the site is now responsive again. Hardly HIGH TECHNOLOGY, but any port works in a storm (and AWS is typically my 'any port').
I've also repointed nameservers to run via a https://www.cloudflare.com/ free account which should provide a reverse caching proxy for the homepage at the least, but will take some time to kick in.
The lesson to learn — one that I would expect most would not need to learn — is that launching a website (even in jest) in a 5 minute break in-between real work with real deadlines is not advisable.
And to second the parent post, I don't feel comfortable with this being posted to HN at all, and certainly not with it ranking #1/#2. I fear someone may have timed it perfectly to start Eternal February.