Then the malware is hiding in the system space, which for some reason takes over 70% of all my available memory.

I’ve heard that as systems update, they keep the old stuff around until you run out of memory. I haven’t checked, and I have yet to reset my phone to factory setting, but if that’s what’s really happening, that’s still unacceptable.

One reason for low memory being responsible for slow loading times, is on the fly (de)compression, to save what little memory the phone has left.