They wouldn't allow it in this society, but I would make the incentives a test of qualities and pay incentive for the genetically superior to mate and the non to be sterilized. Right now, the "incentive" is just a desperate attempt to keep everyone alive.
legalized abortion
This will make little difference. We've already seen that people now are getting tons of abortions, it's not enough. I suppose it may help, but drops in the bucket.
contraception
We have that now, and it puts responsibility on the parents, with a majority not giving a
**** about overpopulation, this is, again, a drop in the bucket.
increased carrying capacity due to infrastructure modernization
It will be an endless struggle, the rate in which overpopulation is going is increasing, meaning, with the methods already mentioned, we would constantly have to upgrade at an increasing rate.
space colonization
Which, for the reason stated above, would become harder and harder. Eventually more and more money will be put into this and eventually it will become so expensive we wont be able to do it.