This is about the future. Maki's Dad's career is still way too unstable right now to set down roots (the terminal project will likely not need his presence for much longer) but wants him to at least consider staying together during university when he might have a permanent gig. He's fully aware that his ex can give him the stability he can't. His insistence that she not work full-time is part of his plan to have his son finally feel secure.
In this situation, it's actually his trump card. It lets him get away with selfish demands. And he knows it. It's the basis of his plan.
So does Maki cut ties officially with his dad later in the light novel?
We don't really see him after LN 2, in no small part because the next point in the story where he might become relevant again would be in the latter half of Maki's third year when university decisions would be finalized, a point that's a full year in the future of both the WN and LN.
I know, the same line in ch29.1 makes equally as little sense to me. Teenagers just don't refer to themselves like that.
