Yar. You have records. Snapchat disappears for users but law enforcement can get logs, including IP addresses. Same with Reddit. If they leak, immediately get a lawyer if you can, or go straight to the cops for revenge porn with every bit of info you have. Even if they're running a VPN there's always a chance they are either using a bad one or made a mistake and there will be a real IP to be found.

Now, I can't tell you how hard the authorities will work on your behalf, but the more evidence you can provide, the more likely they are to follow it through to conclusion. Don't worry about being embarrassed. It takes REAL balls to show photos of your balls to the cops to find the fucker who blackmailed you.

(Edit: typo)