Remove photos from library but keep in an album.

It is not possible, to remove Photos from the Library, but keep them in the albums, because albums cannot store photos. All photos are stored once in the library, and the albums are just linking to the photos in the library. When you delete a photo from the library, it will vanish from all albums.

If you are using iCloud Photos you clean up your library by setting up the Shared iCloud Photos Library. Then your Library will have two compartments, a personal part and a shared part. And when you move photos to the Shared library, they will stay in your albums, but are no longer visible in the personal library, only in the shared library. You can switch between the shared library and the personal library or view both libraries together. You do not need to share your photos to take advantage of the Shared iCloud Photos Library. You can use this on a Mac or on an iPhone or iPad: Using the Shared iCloud Photos Library to have two separate libraries on all devices - Apple Community

The library holds all photos whether or not they are in an album. There is no option to delete them from the library without them being deleted from albums.

There is only one photo in storage and it is displayed in multiple places.

There must be a way to keep them in the album, but not have them in the library?

Photos, (like iPhoto, Aperture, Music, iTunes) is a database. This means it can be very flexible and powerful, if sometimes a little confusing. The library is the core of the app. Every image is in the library. Albums are virtual, and are just subsets of the library. In fact, Albums are not places, they are lists - instructions to the app to 'display this group of images together'. So images do not get "moved" to Albums, they get added to that particular list. This means that an image can be in more than one album but use no extra disk space. Similarly in the Music app, all the tracks are in the Library and can be added to any number of playlists.