If you are using Safestrap, why not put a rooted stock ROM (minus Knox and the OTA stuff of course) into another slot?
I doubt that safe mode will have any effect on framework mods - it just prevents autostart of *market apps*, not where base classes (e.g. frameworks) are loaded from.
You could also install the .apk into an emulator in the SDK, although that is likely sufficiently different from touchwiz that it probably won't provide you with diagnostic info.
"I'm gonna start coding placebo apps. That way I will be sure that the complaints are real and the praises hollow."