Epson default 3880 profiles are not installed in the standard ColorSync directory. They are kept in a "package" that is located at
There you should a file, not sure of the name but it will indicate 3880 ICC profiles. This is a OS X Package, sort of a special folder type. If you right click on it you will see a choice to Show Package Contents, once you do that it will show it's contents. Inside that will be a folder called Contents, open that and you will see one called Resources, and in that you will see the actual Profiles.
There have been occasions where Lightroom won't actually see these profiles because of the way Epson packages them. One work around is to copy the profiles into the standard profile directory
Restart Lightroom and you should now be able to see the profiles.
If you are installing other manufacturers profiles the standard ColorSync folder is the best place for them.
As far as blacks, what paper are you using? I think the 3880 black on Premium Glossy Paper measures about L 4 ... pretty black.