Mold in a sewerage system?? I can't see how that will affect the interior of your house. Lots more stuff passes in the system that would be more degrading, not to mention methane gas.
It seems your sensitivity and active problems with mold are great. I would call in a mold abatement professional and have them evaluate your situation and recommend the best means of ridding your environment of mold.
I don't understand the drastic measure of cementing the shower pit. A judicious sealing of the pipe would have been more in order, and would have allowed the installation of a shower at a later date, which you can't do now.
It seems your sensitivity and active problems with mold are great. I would call in a mold abatement professional and have them evaluate your situation and recommend the best means of ridding your environment of mold.
I don't understand the drastic measure of cementing the shower pit. A judicious sealing of the pipe would have been more in order, and would have allowed the installation of a shower at a later date, which you can't do now.