How can I validate if my App is legal?

Hello everyone, I'm the developer of Almighty: God Idle Clicker. Lastly, we received a lot of modded downloads. After iOS has enabled the enterprise distribution, we are seeing a possibility for mods to be distributed without the jailbroken device.
https://iosgods.com/topic/75493-arm64-almighty-god-idle-clicker-cheats-all-versions-1/

It's just a very first link from search.
On Android, we are validating our App on the server, by sending encrypted sign-key, if the app is signed with a different key, we block the requests from that device but leaving the possibility of off-line play without further interruption of official app clients gameplay.
The problem I have for a nice 2 weeks is to find, a simple way to validate the iOS app on the server. I've unpacked the ".IPA" of modded version and I'm seeing it's "iTunesMetaFile.plist" is modified as well as the package itself contains few extra files, but since iOS 8 I can't access them anymore.
I don't know how to prevent my app from being hacked every time I update it. It's destroying my community as it's a multiplayer based game.
Please help,
Dariusz