Without going through the whole thread: yes, you want to arrive a day early in Sorong. ALL domestic flights are subject to potential delay in Indo. It doesn't matter when you are there for the flight, it's whether the flight goes. It could be a two hour flight and you are there all day, but the flight never goes, so you don't get there. You are getting to Sorong a day early in case there is a problem with that flight. I did Jakarta to Sorong through Makassar because I didn't connect with any flights so if the flight made it, I made it.
They tried to block me from my flight in Jakarta to Sorong on the pretense we hadn't confirmed the flight. Found this out at 5 AM only about 90 minutes before the flight. They wouldn't listen to my Indo travel agent who did book and confirm and only the transit hotel people I had paid to get me checked in saved me by being able to get in the airport and talk to the counter. Made it with minutes to go after they gave em a "first class" seat. The flight back out of Sorong was about 4 hours late. No problem, as I was already booked in the Jakarta Airport transit hotel again to make the international flight the next day.