Going back to your original pics, you show that the water is coming into the footwell from the sill section.
If it's not coming in from the obvious places (front sill plug, door seal, etc.) then it could be workin gits way in through the scuttle/bulkhead where there are several panels.
This may sound daft but (if you can) try parking the car on a slope so you can get it facing uphill, downhill, etc. and see what happens when you spray water where you've said.
That might help to figure out where it's getting in. If that works, it should be possible to seal the problem area without necessarily resorting to taking the wing off.