Sorry…can’t be of much further help here (as I don’t own a Benq Projector)
But I am pretty sure SLIP needs to be disabled; it only allows the board to initiate a connection.
And Benq uses a TelNet connection, initiated from HA.
Also MQTT is not used.
You could try some different GpIO settings:
These are for my ESP01-s, which I use with my PelletStove,
Not sure exactly what settings to use for your ESP12-F 