How do I cope with a job that's nothing like I trained for?

You trained to steward knowledge, and instead your days are spent as a social worker, a tech-support desk, and a shelter of last resort, trained for none of it. That gap between what you prepared for and what you actually do is disorienting, and the exhaustion under it is completely fair. What has really happened is that you became the last open door in a community with too few of them. That is not the job you signed up for, and it is genuinely more than one person should carry. But see clearly what it means: people come to you because you are the one place that never turns them away. That is a heavy kind of honor, and it is also more than you can hold alone. So protect yourself, or you will burn out and help no one. You are not required to be everyone's rescuer. Learn where the real resources are and hand people off to them, so you are a bridge and not the whole safety net. Set limits on what you absorb. And push, where you can, for the training and support this reshaped job actually requires. Caring for yourself is not abandoning them. It is how you last long enough to keep the door open.