Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Mississippi to Africa as you normally would.
Due to the rapidly changing circumstances due to COVID-19, airlines like Delta and British Airways flying from Mississippi to Africa have implemented new flexible cancellation policies.
Yes, there are multiple flights from Mississippi to Africa for under $800. The cheapest flight booked recently is on KLM for just $800, but on average you can expect to pay $1,234.