To fix the front leaf guard, I removed it from the sticky goo holding it in place in the cowl. I then sandwiched fibreglass window screen between the cowl grill and the screen below and reinstalled using new butyl rubber tape, reinforced by small zip ties threaded through and tied to the cowl grill. The window screen has very small openings that prevent seeds, needles and leaf parts from dropping through and allows you to vacuum off the top of the cowl very easily.
The rear trunk lid gap? I have no clue how to fix this. Maybe some kind of stiff plastic tape applied to the underside of the trunk lid might cover the gap.