He puts you through it because he wants the status quo back and he knows that threatening you with your daughter will make you react. He hopes you'll be so scared of his threats that you will come back and everything will be just like it was before.
If it were me I wouldn't even respond to his emails, just save them for court. If you are afraid he will do something like take the baby & run, move her into a different daycare and don't tell him where it is.