You weren't manipulative, you were a good negotiator. You simply used your own knowledge about what his weaknesses and worries and desires were to get what was in your and the kids' best interests. That's what negotiation IS. You weren't a powerful person exploiting a weaker one. You were clever and confident and it paid off, big-time.
I am still blown away by the outcome. Dazzled. And I'm not just saying that.