I'm not sure what you mean by monocultural? Singapore is famously multicultural.
Singapore is very open to foreigners. Almost no one's family has been here for longer than three or four generations. I'm not sure where you get xenophobic from? (However, they do like some foreigners more than others. Just like in the rest of the world, people who came from affluent places to spend money are typically the most welcome visitors.)
Authoritarian might be true, depending on your definition of the world. To call them 'borderline fascist' you'd need a rather torturous definition of fascism (or a generous definition of borderline).
Yes, Singapore is a city-state. For comparison, Berlin and Hamburg are also city states in the federal system of Germany and enjoy considerable autonomy, but with less success. I agree that more cities should become independent and be better run as city-states. London would be an interesting candidate.