What a horrendous experience that must have been, OP, hearing your child asking you to get her and not knowing where she was.
It is easy to criticise the justice system (and I agree, there are many, many things wrong with it) but the real problem lies with using a system that is so expensive, designed for criminals, and so conflict based to deal with family matters. This damages mothers and fathers (and of course children).
But bottom line, once a court order is in place, you can't just stop contact as if it did not exist. You could file (and if you had been able to get affordable advice at the time, might already have done so) for a variation, based on the events of that night and your DD's distress.
Can you discuss the problem with the MIL? (I'd have rung her that night, I think, but I am a cow)
You may have to accept that due to your shock and fear, you may have made a mistake in preventing contact with a significant adult in the child's life (if I have understood correctly that you have stopped all contact) but don't let that stop you insisting that safeguards be put in place to ensure that this contact is supervised by his mother and your daughter is where she is meant to be. (Perhaps an evening phonecall?)