Length of time between RW and this
I think it's about twenty years since the end of RW. RW was in 1997; Canberra was nuked the following year, which was also when Walker took off from Sydney (possibly trying to reach the relatively safe north, like Pappagallo's group?) and crashed in the desert near Crack in the Earth. Slake was born very shortly after from one of the survivors, and Savannah in '99, about the time Walker left. Slade and Savannah are nineteen and eighteen, respectively, when Max meets up with them, so it's 2017.
Regarding Max, he was about 24 in MM (1992), and 29 five years later. This would make him 49 in MMBT, though he looks several years younger.