I'm having a similar issue right now and I'm about to pull out my hair. I've talked to two Apple support guys, neither of which have helped me AT ALL. They only told me to do what I have already done, so I'm not sure how well they listened to me, but they certainly didn't help me (no offense, Apple support).
I have done the "Erase All" option. When I go through the first steps - choosing language, country, wi-fi network, etc., it gets to a screen where it asks whether you want to restore from icloud, restore from itunes, or set your phone up as a new device. I have tried all three. But I want to restore from iCloud with my current Apple ID, not my old one that apparently doesn't exist anymore (so stop asking for it!).
So.. when I restore from iCloud, it lets me type in my current iCloud Apple ID... great, right?! However, once it gets to the menu (all of my stuff shows up, great again!) and I go into Settings > iCloud. it shows my OLD freakin' Apple ID and it asks for my password (which doesn't work). Why is it defaulting to my old, non-existent Apple ID even though I set it up to restore from my current one?! 😠 Same problem you're having. And yes, it still says the same thing at the bottom - that I can't delete this iCloud account because my iphone is being restored. But I can't figure out what the heck is still downloading - by now I have deleted all my apps, my music is all there and fully downloaded... so it must be my pictures. None of my pictures are showing up in my album even though it says that 652 pictures are downloading (it has been two days and not one picture has 'downloaded'). So if it's my pictures that are the problem, fine, although I'm not sure how to get around that. I have read about 73 other threads related to that issue with no resolution thus far. So basically I'm stuck.
I am tempted to hit the Stop Restore button, but I don't want to lose those 652 pictures that are supposedly "downloading." I don't know if I'll lose them, but I'm too scared to find out.
I just don't know what to do. And the nearest Apple store to me is 150+ miles away 😢