Tulips in reference to flight time limitation, CASA would have no say in SIA operations. You will be flying Singapore registered aircraft with a Singaporean license. Therefore under CAAS limitations.
100 hours per month is very realistic. You will be lucky to hit 10 days off per month (not in a row), more like 8 (still not in a row).
Staff travel is a con job. If you buy a interline ticket, you will be told that it is ID75%, but you will pay full fare.
If you get into legal disagreement with SIA/SIA Mauritius, it does not matter that you are in OZ, you will go to a OZ court but follow Mauritius law. Why Mauritius to begin with? Most probably because Mauritius has laws or lack of for SIA to take advantage of you.
Always keep this in the back of your mind, Singapore corporate culture dictates, if they can not exploit you, they do not want you.