My understanding is that the 1000.2 is designed to pick up 129 while the 1000.4 is designed to pick up 61.5. Without knowing a lot about your locations and the line of sight it is hard to say if you can see 12 but it tends to be more problematic than 61.5 in the east.
I use a D500 to split 61.5 and 72 with passable results. Most of the stuff on 77 can be lived without (HBO, Showtime, some music). 72 and 77 are far too close together to get good signal from 77 and 61.5 with a 1000.2 at the same time.