Have you had any luck with sealing the gaps on the side of your garage? The spaces down the brickwork where the light is coming in are gaps between the running channel and the contours of the bricks. You can fill these gaps with a bead of Sikaflex 11fc which is a polyurethane adhesive sealant. It is specifically formulated to adhere to masonry and steel, providing a flexible bond in situations where movement is prone.
We look forward to hearing about the successful sealing of your garage door. Please feel free to let me know if there is anything further you need.