You'll need compressed air if you plan to use a powered tool for wheel nuts. I'd recommend getting an extended bar and doing it the manual way.
We bought this about 10 years ago. One of the best cordless drills we've ever used. Still running strong today. Not sure if the quality has changed but Makita is always our "go-to" for work tools.
Nope. No where near enough torque. And I wouldn't bother with an impact wrench either, unless your a tradesperson (in which case you should already know what one is), as the average DIYer is unlikely to make much use of one. Better to save your money and get a 2ft(600mm) breaker bar.
Shirley this isn't just an "in case" type of hardware.
I got this same set about 3 years ago. I have not regretted it at all.