Anyway, I MIGHT have some not so bad news
The percentage keeps dropping as I use the phone. I already rebooted a couple times before (remember that it has to work regardless, I don't want no workarounds), but I waited many hours before doing it again because I wanted to see if the gap between the real and measured percentage would increase. Well, it didn't. The difference is always around 3/4%. Which is good, and I also checked it by connecting to Coconut a couple times. Also when I did the hard reboot the first time I lost exactly 4%, so probably it was like this even before all of this mess, as someone already hinted.
I'm cautiously optimistic. But I need to wait for midnight in an hour-ish to see if the battery stats will start working again. They didn't with a simple restore, I hope the DFU restore fixed things.
If you want, you can check your battery percentage with Coconut too, the difference should be roughly 4% higher on iOS than Coconut (a friend of mine already confirmed this to me on his too).
Well, let's see