Hi Fëj,
We want you to be able to enjoy playing your game, and we understand that you're still having issues downloading it.
From here we want to restore the device to factory settings (without the backup you will lose data. So verify that you have a newly set up backup)
How to back up your iPhone, iPad and iPod touch
Set it up as new and try to download your game to see if the issue continues there, here's how to restore:
Restore your iPhone, iPad, or iPod to factory settings
We'd suggest following the steps to restore your iPhone and set it up as a new device, just temporarily, to see if the issue occurs without your data loaded to the device.
When you set up your iPhone you can sign in to iCloud to sync Contacts, Calendars, and other information, but we want to be certain there's nothing in a previous backup that could be causing this behavior.
In the meantime, have you tried to download while being connected to a good known Wi-Fi network?
Thank you for using Apple Support Communities. Have a nice day.