I see the wisdom in your choice not to get your child given he may have COVID.
Most single parents--moms or dads--if they've been vax'd are capable of caring for a child while sick--especially with the invention of Doordash for grocery and meal delivery. If you're unsure about his ability, consider a daily check-in with him and your son.
If he loses the capacity to care for your son, I agree with DV, take your son away from your XH. That minimizes the chance of you, your son, or your newborn being infected. XH chose to fire you as his wife. One consequence is not having you as his wife!
