Fix leak between seal and shower door joint
you could always cut a small piece of urethane or silicone foam (closed cell only) and glue it into the gap on the static side of the opening.  it would act as a live seal that could adapt to the gap or move as the door rotates.

you might want to take some time to really clean the existing sealant/caulk out from all over and redo it.  also do the floor to shower pan joint.  use a good solvent to clean everything up and bleach all surfaces prior to re-caulking.  you have so much filth and mould there that new sealants wont stick.  a properly sealed shower assembly wouldnt let water into your ceiling below even if the door seals are not working.