This marks three days of disservice (Friday, Saturday & Sunday) as a Network Engineer myself I honestly can't understand what's taking you so long.
Any proper service provider (Azure, AWS, Cloud Flare) would've intervined in a two hours SLA, my only explanation is that you either have the servers in-house (maybe rented a small space in Aruba) and don't know how to handle a DDoS attack on your own Firewall or got a very cheap service provider (which doesn't know how to handle DDoS attacks).
Either way it doesn't matter, so far you have two healthy servers, a chance to grow a game that even though is old has a very stable player base (as your servers & hundred of private servers show).
That this means? It means that you'll keep getting DDoS attacks, your servers take business away from other servers, you need to scale up your infrastructure and get a proper protection service with a very small SLA (which means investing money and resources to then have a pay back).
If this keeps going no matter what compensation rewards you give, people will leave, once people leave getting them back is extremely hard, then it's a chain reaction, people leave because they see other people (& friends) leaving, servers die, income slows down.
I know I'm probably better off talking to a wall, since nobody with any decision power will read this, however, you guys have a chance and you're screwing it up spectacularly (keep in mind that no other game service provider has DDoS issues, I only ever saw those in private servers, which speaks volumes about the service you're providing).