Admittedly I skimmed that. Something stood out though.
"I feel like detachment to me IS withdrawal."
Withdrawal is making yourself unavailable to someone physically or emotionally. Detachment is not allowing someone else's actions to affect you whether you're available to them or not. You can care for someone without letting their actions affect who you are and how you behave.
Me: 31, W: 29 T: 4 M: 2 Kids: 3 (SS: 7, SD: 4, D: 3) Separated, still living together: Nov 2013 Separate bedrooms: Feb 2014 W working away; kids with me: Nov 2014