I would say book a flight now for April (couple days before the visa expiry date) and also buy the insurance.Yes it should change to we are reviewing the additional documents, but that will change when officer looks into file.
I hope the officer looks into it soon. It is so much of a dilemma as what to do. Booking the flight and then cancelling later is a waste.
Insurance will cost you maybe $100 max but if you get everything done before the expiry date then cancel the flight.