Evaluate the whole situation and do what's best for you. You already know that the primary contractor wants you to stay because that's best for themselves, so

Evaluate the whole situation and do what's best for you. You already know that the primary contractor wants you to stay because that's best for themselves, so they are not an unbiased opinion. If you've conveyed to them that the likelihood of meeting the deadlines is small, keeping you around gives them someone to shift the blame to when it's missed. If you've raised your concerns about the work, and they can't bring in additional help to meet the deadline or are unwilling to adjust the deadline, then there's no more for you to do. Chaos from you leaving, budget cuts, or just poor project management are not your concern.