Sorry I've seen too many of these childish arguments..... the underlying "hope" is that one would simply do nothing and untold riches would fall from the sky on one's head if only......one gained independence
You're familiar with the situation in sub saharan Africa and you know this is not how it works.....
If you're saying something different, you could state it more plainly or unambiguously.
Family support or a good family environment will be affected by adverse economic conditions, but honestly I don't know what all of the exact causes are. I do know that the indigenous people were excluded from the economy for a long time, deprived of land, and put in reservations, so they should have a whole lot of catching up to do.
Regarding unemployment, the Kanaks (the actual indigenous people) have an unemployment rate that is much higher than the other groups.
15,000 unemployed in New Caledonia
So the 12% is not representative for them.
As for the rest of what you've described, it seems like New Caledonia's education system might be a failure in general, not just in Thio. Most of those diplomas don't seem to be going to Kanaks.
New Caledonia's Kanaks disadvantaged
In which case their being subsidized clearly hasn't achieved much for them. 85% of the prison population is also Kanak though they are around 40% of the total population.