The Photo Library has become unavailable or it's data is corrupt

From the point of problem today which just suddenly occurred...

Maybe after I tried saving a picture to Photos or trying to attach a picture to an application (Messages or???). I can't remember what started it or what I did.

Photos will not open on my MBP.

I get this:

After following the steps:

If you're having other issues with Photos

If you're experiencing other issues—like missing or blank photo thumbnails, unexpected behavior, or if Photos won’t open—you can repair your library using the steps below. 

The Photos repair tool analyzes the library's database and repairs any inconsistencies it detects. Depending on the size of your library, this might take some time. When the process is complete, Photos opens your library.

Follow these steps to use the Photos repair tool:

1. Make sure that you backed up your main Photos library.
2. Quit Photos if it's open.
3. Press and hold the Option and Command keys as you open Photos again. 
4. The Repair Library dialog appears. Click Repair, and then enter an administrator password to begin running the Photos repair tool.

I get this:

This hangs at 7% for about 30 seconds and then goes back to the first image.

I created a second user account. Opened Photos, imported a few pics and it works fine. I did not connect or link it to iCloud, the current Photos Library or the Photos Library from TM backup.

So I don't think it's the Photos application.

My photos in iCloud are visible from the devices.

The photos are visible within the Photos application via Finder on my MBP.

Pictures>Photos Library>(Right Click)>(show package contents)>Masters

I've copied this Photos Library to an external drive for safe keeping. These images are visible when opening them using Preview.

I tried restoring from TM back up from 10 days ago. The same images as above.

At this point I have deleted the Photos Library and replaced it with the one I copied to an external drive and deleted various Photos .plist files and have probably really jacked things up.

I only use Photos for pictures I have recently taken and want to use on the iPhone. If they are seriously important and/or keepers, they are exported and saved in other places.

So, all the current pictures/movies that were in Photos I could sorta do without. I have copies from when I copied the Photos Library earlier AND a TM backup from 10 days ago.

What do I need to do to get Photos working normally again?

Go slowly and descriptively, I can follow detailed instructions.

Thanks.