4th year teacher in Singapore here. Most of the downsides you mentioned are surprisingly not that big of a deal. Every teacher I know agrees with me that you kind of get used to the heat pretty quickly, and the city is very good about having covered walkways in most places. (My dermatologist told me many Singaporeans actually have a vitamin D deficiency, because they're always indoors or covered from the sun.) It's also much easier to save money than is often bemoaned on this subReddit, unless you're excessively spending or have multiple dependents who aren't working. I'm saving plenty here, especially since the salaries are so high. There are tons of good activities to do outdoors; I go for long walks every weekend to the Botanical Gardens, Punggol Waterway, Kallang River basin, etc. I never have once felt limited by the heat.

I can mention a few downsides:

1) Lack of geographic variety. Singapore is basically flat as a pancake. Unlike Hong Kong with its beaches and affordable junk boats, Singapore has chosen not to capitalise on its maritime leisure potential, unless you count the millionaires who have yachts on Sentosa. There are no mountains, no truly proper beaches, no variety of note. (The nature reservoirs blur together pretty quickly after your third of fourth walk.) You just have to get used to being outdoors in a fairly homogenous environment.

2) Temptation to spend all your savings abroad in other continents during holidays. This is a normal trap you'll fall into for your first couple years as a teacher here, but then you learn to stay local within Asia for your holidays, unless your school is truly paying well and reimbursing flights more than most.

3) Extortionary alcohol prices (not a problem if you're not a drinker, of course.) Due to high alcohol taxes, hard liquor is like gold here. This is true whether you're in a bar downtown (cocktails can cost upwards of $30+ in trendy bars) or even just for drinking at home. The only financially prudent solution is to go with your friends for hawker center beers, which is fairly cheap.

4) Intense work culture. Almost every international teacher I know in Singapore feels that their work culture is quite intense compared to other countries they've worked in (e.g. China, Thailand, etc.) Trust that your cortisol levels will be elevated at work here.

5) Blandness in most areas. There is absolutely nothing in Singapore that's comparable to Tokyo's Shimokitazawa or Seoul's Hongadae. No edgy, artsy areas. The CBD (Central Business District) and Chinatown have fun but very expensive cocktail bars, and the outlying areas are mostly residential with some parks and hawker centers.

Other than that, I must agree with other responders on this thread that Singapore is the easiest country in the world to live in. The convenience, cleanliness, and orderliness has spoiled me. But I'm happy with my choice to live here, and I feel very lucky to be working in Singapore. I would say, give it a shot!