Yep, the diagram in post #4 made it very easy to see what is where. I'll walk through the pictures to help you understand what is going on.
Pic 1 (mentally rotate 90° CCW to match the digram) - this is a diplexer, in this case being used to break out the Sat and OTA signals. The line labeled "goes to TV1" actually goes to the other diplexer (they're typically used in pairs) shown in Pic 2 which goes to the Sat rcvr. That line is carrying 2-way traffic with the sat feed coming in and the TV RF going out.
Pic 2 - the Input of this diplexer goes to/from the other diplexer in Pic 1. The Sat output goes
to the DPP Separator in Pic 3 and 4. The VHF/UHF output is actually coming
from the receiver's Home Distribution, pretty much as stated.
Pic 3 - the DPP Separator, signal comes
from the diplexer in Pic 2 then on to the Sat1 and Sat2 inputs on the receiver. The Separator is actually a special use case of a diplexer, this one breaking out the regular DBS and higher band-stacked
DishPro frequency ranges, as opposed to the regular diplexer that combines or separates the DBS and OTA frequency ranges. You begin to see why Dish gave it a different name.
Pic 4 - showing the lines at the receiver that connect to the diplexer in Pic 2.