As stated by others, island dwarfism or selective breeding could explain the Goblin's size not growing past that of an ordinary Homo Florensis.
Their big noses and ears could easily be explained by living in a dark area;
Nixoncranium mentioned dense jungle underbrush. I would like to add caves, though, because small size would be an advantage when chasing prey through small tunnels and eyesight would be practically useless there.
While eyesight would be pretty useless in caves, hearing and scent would be incredibly useful; as evidenced by the Crawlers in The Descent, who navigate almost solely by those senses.
Their poor eyesight can also be explained by this quote about bat's sight from usgs.gov: "No, bats are not blind. Bats have small eyes with very sensitive vision, which helps them see in conditions we might consider pitch black. They don’t have the sharp and colorful vision humans have, but they don’t need that. Think of bat vision as similar to a dark-adapted Mr. Magoo (a cartoon character with very poor vision)."
Finally, caves are relatively scarce in resources, so the goblins will likely go foraging. This makes sight useful and therefore ensures it will be retained; but since sharper eyesight isn't an advantage in light-poor caves, it will remain poor throughout generations.
Green skin could be explained by:
Fungal layer-Caves come with fungi, it's quite plausible that the goblins, due to an unsanitary lifestyle, are coated in their very own layer of fungus.
Vestigial trait-Perhaps one of the Goblin's ancestors ended up with green skin and the Goblins kept it; it didn't hurt anything, so it stayed (like the vestigial claws on pythons).
Camouflage-When Goblins go out to forage the forests around their caves (I assume there are forests around their caves) green skin helps them blend in. This mutation arose out of nowhere generations ago, and since it kept the goblins who possessed it alive (as opposed to pale goblins, who stick out like sore thumbs except on, say, snowy mountaintops.)
Pigment Retainment-Perhaps the Goblins eat an awful lot of plants and green fungi. Regular humans can turn orange by eating an awful lot of carrots; a similar phenomenon could make Goblins green.
Their quick transition to adulthood could be explained by a harsh environment that makes lifespans relatively short for the vast majority; look at humans in the Dark Ages, which rarely lived to forty, or even thirty-two. The Goblins that reached sexual maturity faster were the ones who had offspring before natural selection got them, so that trait was found in all the survivors.
Later on, the Goblin's growing intelligence increased their safety and quality of life (and therefore their lifespans), and the Goblins who lived longer had more offspring, therefore outcompetiting their shorter-lived relatives. Finally, longer lifespans didn't cause a resurgence in slower-maturing Goblins since that trait had been (quite literally) killed out of the gene pool.