Hi,
I am just a laymen but had been posted to HK for a short stint.
Here are some considerations
- housing allowance
- hardship allowance
- home leave allowance
- children education
- personal tax issues (how much are you being disadvantaged)the difference need to be top up
- Foreign exchange risk (may need to consider pegging the US$ against S$ as much of the expenses has to be incurred in Singapore.
As for rental, with that budget your should be comfortable - again depending on the location, type of housing (apartments, condo, or house) your choose. I have noticed that you do not intend to get a car and hence the vicinity of your housing location and where you husband commutes to work would have an important bearing.
Cheers!!!