Full Fact

It's correct that 2015 saw the highest level of house building in a number of years. Around 143,000 homes were completed in total across England. The last time the figures were that high was in 2008. This is still low by historical standards, though...
We can't say that homelessness has been reduced by 67% or any specific other amount because the Welsh government has changed what they do about homelessness and how they count it. This isn't to say that the changes haven't made a difference; just that we can't put a number on that difference at the moment.
We don't currently live in a country that practices population control, and the poor children that the government seeks to punish simply for existing are already here and a part of our society. We can't send them back, nor should we wish them away.