There was no way “A Gettysburg Address” could have been as riveting as last week’s “Q&A,” but it still gives viewers enough to chew on to keep them more than invested. This week’s installment of Homeland raises a lot of interesting questions now that we’ve reached the middle of this stellar season, not the least of which is whether Brody (Damian Lewis) can be trusted, or whether his alliances still lie with Abu Nazir (Navid Negahban).