You might get away with the coating on the air box, but that crack you filled looks real scary. Is the car straight, frame wise? If it is and everthing else is solid I'd still weld in patches as a minimum. That's a stress area, between the A pillar and door hinges and I don't think that plastic will stay for long. Remember that whole area is vital for the structural integrity of the car, Better to fix it now before you finish it and have problems later!