2: strongly disagree; I use Firefox, and on the odd occasion where I’m doing something in Chrome, it drives me insane with things like its CSS editing experience, because it does things in what I find to be a much less native-feeling way, whereas Firefox’s behave in a mostly native way, so that things tend to work the way I expect. There are glaring problems with it (mostly around “completing” a whole new word when I press Space when that makes an otherwise valid value nonsense; I really should file a bug about that if there isn’t one), but I find Chrome much more painful to interact with. And what do you know, a lot of it probably comes down to familiarity and what you’re used to.
3: Chrome is a disaster for large numbers of tabs. On most screen sizes it’s just about hopeless with even thirty tabs, maybe as few as twenty, both for reasons of performance and because of its infinite tab shrinking folly. Firefox, on the other hand, can handle hundreds of tabs in a session with perfect equanimity (though performance will definitely be affected by that point).
On DuckDuckGo, I find it to yield good results most of the time, and it’s rare for me to reach for !g.
In most of these sorts of things, it’s much more about what you’re used to and know how to interact with, than any inherent superiority of one over the other.