Oh man, I don't envy you at all.

Do you have any pets? Flea's have trouble surviving on people alone, I'm surprised one held onto the boy for so long.

Are you sure it isn't a bed bug?

She needs to treat everything before the child comes back to care you need to inspect the child upon entry.

Regarding termination... I don't know. I think that sometimes you just terminate in fear that something worse may happen. I think you need to break ties with this family some how. But not sure how.