Sorry I didn't read all the posts, so if I repeat or missed something, plz forgive me.
to OP, I will have to agree with theBrit. If the main motivation at this point is money. I'd say, stay in Singapore.
Ur wife's health is far more important and the schooling issue for your kids will make ur hair turn white.
But if it's more then just the money, if this is a way to fast track ur career, so u can make MD faster here then u would staying in SG, or ur dying a slow death at ur current job... It's tough choice. Talk it over with the mrs. and work on a plan B.
Plan B might be like, if it doesn't work out...your family goes back within 12 months, and u start communting after that as mentioned by others until u can find an even better job in SG.