HELP: Popup is preventing my app from starting! (iDownloader PRO v 1.13)

Hello, I'm currently using this app called iDownloader Pro v 1.13

It's a downloader app that lets you browse the internet and download various media files (photos, pdfs, etc.) and lets you keep them organized. I have over 16GB of files within the app and I am unable to launch it now because this website I was browsing initiated a popup for some fake apple customer support (that scam stuff). Anyway, it happened while I was using the app's built in web browser. I have the app password protected, and so whenever I try to start the app up, the popup appears too fast for me to be able to put my password in to even access my app!

So far I've tried:

- Closing the app and opening it again

- Restarting my iphone

- Trying to restore my iphone from a backup (failed because "there's not enough space" on the phone)

- Enabling airplane mode and then trying to use the app

In short, does anyone know if there is a way to close the window in iDownloader's internet browser that is causing the popup? I can't even access the app because the popup appears so quickly that I can't do anything!

NOTE: I am NOT on the most current iOS version (which is 8.4.1 .........I'm probably 8.3 or something right now)