I loved what you wrote about your birthday dinner with your wife:
That getting on the rollercoaster was worth the price of admission.
No one claimed to remain emotionally stable and predictable during one of the most stressful experiences in life, much less the individual who decided to step away. Think of the emotions that cycle through you in a day and multiply by 2, 3, 4.
The one who leaves has to justify their departure, something that runs contrary to their beliefs, especially when children are involved. They have to build a wall between them and their spouse to allow this change to occur.
I know when I talked to spouse today, everything was about him, how he sucked it up while we were together... it was the HIM show.
Your wife is opening to you, then getting scared. Think of a sea anemone.. whose tendrils are so lovely but swoosh back in at the sign of danger. She's swooshing now after enjoying her loveliness.
There's no doubt you're a great guy who is making her feel comfortable enough to relax at times. She still has the old messages looping through her brain. Who knows if she can change them, but you're playing a tune she wants to listen to.