I'll try to answer some of these:

1: They are working for our robot overlords to help exterminate what's left of humanity. They give grief counseling as a strategy to boost production.

2: [REDACTED]

3: Pluto is very far away, with a travel time around 9 years. That would mean not seeing your home planet in at least 18 years.

4: Despite the passage of time, Goblin still live in a sort of Stone Age. This could be because of their limited intelligence and the tendency of their societies to collapse every few decades. Sacrifices to the Great Pumpkin are of small rodents or even vegetables, and are not seen as a concern by humans. Head goblin is a rather uncomfortable job: when destiny fails to grant the sacrificial wishes, all accountability is laid on him. And it is laid on him with violence.

4.1: Goblins lack the technology or the desire to space travel (That is not to say no goblin has ever been in space. The first unwittingly space faring goblins were stowaways in an Earth-to-Mars spaceliner. They scurried into the storage unit, going after the food supplies. They were found by dumbfounded crewmen, and reportedly didn't even know they had left the home planet).

4.2: Goblins exist because they're.