Photos Library on External HD, appears corrupt, won't allow me to transfer anywhere

To copy that Library from the damaged disk try use a back up utility to make the copy for you. Something like Carbon Copy Cloner or any app that makes a direct copy of the item, not that packages into its own format like Time Machine does.

Have you told us how your drive is formatted? To avoid damaging the Photos Library an external drive must be formatted in either APFS format or Mac OS Extended (Journaled) format. Additionally, the drive can not have had Time Machine on it since it was formatted. And the drive needs to be connected by cable to the computer, not networked, clouded, NAS, etc. There have been so many problems with using incompatible drives that the newest macOSs won't even allow a Library on a non-Mac formatted drive to open, since there is a chance of damaging the Photos database. See this:

Move your Photos library to save space on your Mac - Apple Support

If this drive is in a an incompatible format, stop running Photos with it immediately! A Photos Library can sit on an incompatible drive, but running it may corrupt the database.

As far as copying goes, I used TeraCopy when I was grabbing old backups from CDs and DVDs, because it doesn't seem to hang up on files it doesn't like. It doesn't get great reviews at the App Store, I notice, but it worked for me.

I've had trouble with docks and USBc-- I'd try connecting directly. I've also had trouble with USBc cables-- some are really made for power, and they don't work for data. I've thrown away several.

APFS is generally better, and much better with SSDs. It shouldn't matter, but if it's no trouble to re-format, it's worth a try.

I recently bought a couple of 10TB mechanical drives for backup, and I'm amazed at how slow they are! I mean, when I only needed a terabyte or two, it was OK. But now I'm thinking that when you have a so much data to move that you need a 10TB drive, it just might be better to go digital.

Just thinking…

The Photos Library is in a "package," a special folder that keeps all the parts together so that the database can find them. The "package" is designed to be a bit harder to open so that people won't accidentally disrupt the database's ability to communicate with its parts. The Library can't be used laid open like that.

If you can't get the library to work, then you can at least recover the originals from the Originals folder. (Other folders, like Resources, may have low resolution versions.) The filenames will be confusing. Since so many photo systems use similar naming protocols, there could be a whole bunch of IMG_0123.jpg files, for instance, so Photos renames them with filenames that are very long and nonsensical, but which are unique. Without the use of the database, you're stuck with these names. Everything else about the pictures inside are just like the original uploads, but all edits are lost in the database. If the database was corrupted, as seems likely, then this is the best you can do without backups.

You probably ought to try copying again, perhaps with different apps.

Cloning, as recommended by Yer_Man should allow you to copy the library as it is, but you might still encounter errors, when you try to repair with the clone. If you still cannot work with cloned library, you can open the package and copy the subfolders separately out of the package to a new folder. This way you can check, which files are causing the error message and skip them when copying and recreate a working library. I could save some of my libraries by copying the internal files separately and managed to save the structure of the library, not just the original image files. Since Photos 5 on Catalina the originals do not even keep the original filename.

See this user tip: How to avoid the Error -36 when copying a Photos Library - Apple Community