Lapita Goods and State: True, obsidian and shells probably won't cut it as a major trade goods. But what about other readily available trade goods, such as pearls and coral? If you're not looking for luxury trade goods, then crops could easily cut it as well. And another possibility, ITTL, you could alter Lapita cuisine to make spicier food more popular- as such, they could easily start cultivating and trading nutmeg and mace within a few hundred years of their arrival, using the Myristica argentea species exclusively native to PNG and the Bismarck archipelago instead of the Myristica fragrans variety exclusive to the Banda Islands, pipping the Banda Islanders to the post by several hundred years, and securing their status as 'the Spice Islands' of TTL instead. And if you do, then there are your trade links with China, India and the rest of the world, completely secured until you reach the era of European plantations.
Galapagos settlers- it'd be a lot more plausible for the Rapa Nui, since they'd be going with the current instead of fighting it all the way- for the Hawaiians to have stood a chance of getting there, they'd have had to follow the currents down past Rapa Nui and make their way back up from the south anyway.
Religion- Maybe. If you went with the alternate Spice Islands option, then you would certainly have missionaries and the like coming along with those traders and merchants. But unlike the Banda Islands, its location's far more favorable for the East Asians than the Arabs, so you'd be far less likely to have Lapita Sultanates. Of course, the question is, which East Asian religions would have been proselytizing enough? And what sort of competition would they be going up against- what would the indigenous religion, or religions, of the Lapita peoples look like by then?