I really sympathize. This sounds extremely frustrating. A tactic that has helped (as a T.A. last term) was surveying students.

Ask them about what they’re experiencing right now, what obstacles they believe might come between them and optimal performance in the class, what their expectations for the course are, & what they might be worried about or have questions about. Expressing your own concerns to them about their ability to participate, and also expressing your own struggles or concerns about the current term, will help build trust and mutual engagement.

I know it’s not ideal right now but so many students are struggling outside of their academics, and a tiny bit of outreach at the beginning of the term will help both parties feel better & have a clearer of idea of what’s expected and what’s possible.

Having a punitive exam and setting students up to fail will not create a safe environment for learning, nor will it do anything to make you feel better about the status of your course. Good luck and again sorry to hear that. Know you’re doing your best and it’s a horrible time to be teaching right now. Acknowledging the many layers of added stress and pressure on ourselves, helps