The "filed_departuretime" represents the time the flight is intended to depart. If you want to know how late it will be, you can compare (filed_departuretime + filed_ete) with the (estimatedarrivaltime). Note that you will need to look up some of those additional fields using FlightInfoEx, since the Scheduled function does not include all of those values.
If you want to know the other codeshares that a flight operates, you can use the AirlineFlightInfo function to find that.
We do provide a sample FIDS that uses FlightXML, which might save you some implementation effort:https://github.com/flightaware/FlightXML-FIDS-PHP