5. If Singapore is indeed a "gold mine" and land of great opportunity for these migrant workers, why should the migrant workers want to openly "revolt" in Singapore and to destroy their own hopes and their own land of opportunity in Singapore, in the first place, please?
That is exactly the point. The reason there is no civil unrest is because everyone is making money. If the Singapore economy takes a nasty turn for the worse (and I bloody hope it doesnt!) then PAP is in trouble.
The Chinese Communist Party in Shanghai and Beijing are also all too aware that their continued grip on power is dependent on continued growth - so long as the middle class feel they are advancing then the democracy riots of Tianamen Square will not spread to the middle classes. Heaven help the CCP if the boom goes bust though. If there is anything that keeps Wen Jiabao awake at night it is worrying about an economic slowdown. And that also explains why they are too afraid to enforce existing environmental standards.
I will be ironically amused if democracy requires a recession as a catalyst. If I had more time I would like to go and check whether you could link recessions with transitions to democracy in the Western world - ie Boston tea party, French revolution etc.