When Ellie discovers David's true self, she has to grow up even faster. She goes from a somewhat naive girl in that situation to a survivor who will do whatever it takes to get out alive. Her interactions with David force her to face the worst of humanity, which in turn shapes her into a more cynical and yet stronger person. For example, she may become more decisive in her actions and less likely to give people the benefit of the doubt in the future.
One heart - wrenching scene could be when Ellie realizes the true nature of David. It's a moment of shock and horror for her. She has to quickly shift from perhaps seeing him as a possible ally to a dangerous threat. This realization that she has been deceived in such a cruel world is very impactful.
The story of David shows us the power of faith and determination. It teaches that with belief in God and a strong will, one can overcome great challenges.
I'm not sure which is the very last David Sloane novel as there may be new ones in the works or I might not be fully updated. You could try checking the official website of the author or major book retailers.
The Last of Us was not a comic originally. It was first developed as a video game, which gained significant popularity and later inspired other related media, but the comic came later.