iCloud Photo Library stuck on 1%

So, my iCloud Photo Library has been stuck on 1% for over 3 months now.

The iPhone storage on the phone is 64 GB, and it says 21,6 GB of that is being used.

My iCloud storage is 2TB, and it says 13,1 GB of that is being used. This is after I've deleted almost all my apps, the only ones remaining are the ones that can't be deleted, and Messenger, Notes, Calendar and Contacts.

When this all started I was getting these two messages:

1) "Storage Almost Full, you can manage your storage in Settings" and

2)"Not Enough Storage..." with the options 'Close' and 'Upgrade Storage', at which point I upgraded my iCloud storage to the 2TB I now have.

The very first thing I tried was the good old "turn it off and on again", nothing changed.

In Settings > My name > iCloud > Photos, I have "iCloud Photo Library" and "Upload to My Photo Stream" on. I've tried turning these off and on again too, without results.

I cannot delete any of my pictures or videos from my phone. When I try, they only reappear again a minute or so later. I can’t take pictures or videos, if I try my phone freezes and I occasionally have to restart it.

I don't have a Mac, I recently had to buy a new computer, so I'm using iTunes on an Asus. I've logged into iCloud via my computer, but none of the pictures and videos I have on my phone can be found anywhere in my iCloud Photos.

In Settings > My name > iCloud, I've currently turned iCloud Backup off to see if that changes anything, but it hasn't, so I'm planning to turn it on again after I've posted this.

In Settings > General > Reset, I've tried "Reset All Settings", which didn't change much at all.

I've yet to try "Erase All Content and Settings" because I'm afraid that'd make me lose all my pictures, videos, contacts, notes and text messages I need to keep for informational purposes.

I've done one backup via iTunes on my new computer. I regularly did backups on my old Mac, but it crashed last December and is unsalvageable (I got some help on the Apple forums with it, but nothing more could be done).

I think I've listed everything I've experienced and done so far. Anyone got any suggestions whatsoever of what I can do to fix this issue, without having to “Erase All Content and Settings”? I’m saving that as the absolute last resort.

Thanks!