A:AnswerNo, it's not waterproof.
The only weather resistant power banks I know of just have protective covers over the ports. The ports still cannot be wet on those units.
A:Answer5 x's 2.4 = 12 watts / 2 ports = 6 watts per outlet. Times probably about a 65% efficiency factor = about 3.9 watts per outlet if the manufacturer isn't telling any fibs.
Retired EE.
Yes chargers are rated in watts.