2. A few degrees the wrong direction and the whole globe turns to ice.
3. A warmer earth with more carbon increases crop yields and actually has positive effects. The downside might be people need to move inland.
4. Much more concerning is the chemicals we are releasing into the atmosphere — I’d be seriously concerned here.
There's a lot of human suffering underneath that anodyne phrase. Deadly storms and refugee camps and all the rest.
The trouble isn't the final temperature, it's the speed of the change. Given tens of thousands of years ecosystems can adapt. Change the climate in a few decades, though, and many species will just die. We aren't going to know all the consequences of that biodiversity loss until it's too late to fix.
You're absolutely right however that there's a narrow band of temperatures consistent with a habitable Earth. Which is why research into tools we might need to stay in that range is a good thing.