After spending over a hundred hours, maybe close to or over two hundred, delving into what was happening and trying various approaches/fixes to deal with the onslaught of bots, the site seems more stable now and responsive. Fingers crossed.
One necessity was banning entire swaths of internet IP addresses. Mostly large chunks of China/Asia, as well as other subnets that either have cloud centers hosting sketchy/malicious bots, or known to have large numbers of infected consumer equipment.
I tried to double check ahead of time that none of these subnets had active HFU users, based on their recent IP addresses.
It's possible over time that some users will get migrated to new IP addresses in blocked subnets, so if your ability to access the HFU suddenly vanishes, you know why. I don't think this will affect users in North America or Western Europe, but could affect some in Eastern Europe or Asia. You might need to use a VPN if that happens.
Speaking of - This may also affect those who use VPNs to access the HFU - if you're affected, try adjusting your VPN settings to get to an unblocked subnet.
It's unfortunate that these changes had to be implemented, but as I am sure most active HFU users are aware, the past two months (or more) it got so bad that at times the site was unusable. Half a loaf is better than none.
As with so many things, we can't have nice things because a small percentage of people are jerks.