Can this 35lb mirror mount on this wall?
Those apear to be Tapcon type screws with 2 there should be no problem supporting the load. I would probably add a washer to each screw so the wire cannot jump off the head if the mirror is adjusted. I would not worry about trying to fill the hole around the shaft of the screw it will support the load and if filled when removing the screw at a later date it may break the plaster.