Do you still have the source photos outside of the library?
There is a way you might be able to do what you want more easily. k
1 - go into the Import view and select all of the photos you just imported.
2 - export them as originals to a folder on the Desktop. Name the folder what you'd like to have an album named.
3 - delete those photos from the library.
4 - drag the folder of photos onto the Photos icon in the dock.
5 - in the Import window check the "Keep Folder Organization" checkbox.
6 - import all of the photos.
7 - look for a new folder in the sidebar with an album inside. That album will have the same name as the folder on the Desktop you imported. You can move it to anywhere you'd like in the sidebar.
Another problem, I have many old folders of photos, in which the photos have vanished. The only thing in the folder is DS_Store.
These are folders on your hard drive, not in the library, right? You shouldn't be seeing the DS_Store file as they are invisible. Why those folders are empty I have no idea. Are they the folders of image file you imported into the library?