iPhone: Undo "Optimize" photos? Download and store originals not working?

Yesterday I was approaching 127 GB of 128 total. I accidentally hit optimize photos. I did not want to do this. at the time, I was in the basement of a hospital and did not have service. No service. Instantly, within moments, my entire photo library was reduced in storage size by about half.

Is there a way to undo this?

This is awful, high resolution pictures that I need, brand assets that I use daily, not only were they turned to low res, some seem to have not even saved the same images (one of these I had cropped like 8 months ago yet it is saved locally on my phone as a uncropped version now... ??)

iCloud photos is on. Has been for months.

iPhone 6.

Ios 12.3.1

I want to restore all of The originals.

Honestly I wouldn't mind resetting my iPhone because system/other has ballooned up to 20gb (?)

What should I do?

I really just want to download and store originals. currently, download and keep originals is checked. Optimize iPhone storage is not checked. This phone was on my charger on Wi-Fi last night and I thought it would download and keep the originals. It did not. The storage has not changed at all indicating that any originals were downloaded overnight.

To my knowledge, my backups on iCloud are current. It shows last backup as yesterday, but it only says 6.49gb. under iCloud, I'm seeing only 63 gb by photos, but I thought it was more the day before! My phone shows 40.81gb by photos under general>iPhone storage

Should I reset the phone, hoping it will clear out some of that system/other garbage, assuming that it will download and keep my originals moving forward?

How do I restore The originals?

If I start deleting local iPhone files, does it delete them on iCloud?