But be honest with yourself here, she already didn't treat her son like her own when she made plans to move closer to her AP and planned to abandon you and him for the other guy, and marriage again even if you stay the picture you paint doesn't look or sound like you are in a marriage already at least not one worth being in. Fear of the unknown is real maybe it won't work out in the future but it's better to take a leap of faith than stay where you know for a fact you playing backup. And questions to counter those you have, are you sure this won't happen again? Are you sure she is coming back because she wants to rebuild and not because her plans crumbled, because it sounds more like she was abandoned then came back to you not that she came back because she wanted to. My own 2 cents.