I am still inclined to think that the Titan has been destroyed, although I hope I'm wrong. As far as the 7 ways to surface in an emergency, I'm not convinced that the engineering is good enough for any or all of them work. If the "deadman" method - the release by rope that would deteriorate in a certain timeframe - worked, the Titan would be on the surface. If it is submerged, but near the surface, that is a sign of poor engineering that did not account for water temperature and other factors affecting buoyancy.
Although the timed underwater noises/banging were very encouraging, it is also possible that these noises were emitted by surface vessels in the vicinity, and don't originate deep underwater. That problem occurred during the MH370 search.