When it comes to a leaking shower pan there really are no other options. The leak is actually under the tiles where you cannot access it. The bulk of the water drains in at the top but a good amount passes through the grout to the pan where it drains through the weep holes into the drain.
If the drain is at all slow snaking it clean may help somewhat but don't expect miracles. The deposit that you see on the pipe is the mortar base and grout deteriorating.
I can't blame you for the multiple postings though...
I wouldn't want to hear the message myself...
I would highly recommend the Kerdi System I linked above and the John Bridge Website is by far the best tile information site on the web. John Bridge wrote the book on Kerdi Showers see the link below.
http://www.kerdishowerbook.com/