If filed via Premium Processing, case decisions take 15 days from filing.
If you already hold H-1B status and a change of employer, you can begin working for the new employer the day the petition is received by USCIS.
As long as you have a valid H-1B visa with which to re-enter the United States, international travel should be fine. If you do not have a visa, it is not recommended as it can be difficult to obtain a visa interview with a pending case at USCIS.
H-1B petitions can be approved in 3-year increments, up to a 6-year maximum. However, you can apply for extensions beyond the 6-year maximum if you have an approved I-140 but are not current to file for Adjustment of Status.
Yes, your spouse and children under the age of 18 can join in H-4 status.