It makes some sense that this recovery is more difficult as it is a redo. I know that each additional Nissen surgery is more complicated, and it certainly could make the recovery more challenging. Everyone's situation is different and all of our bodies have unique ways to respond to the challenge of recovery.
This time you didn't "just" have a wrap created, but also had a take-down of your old wrap, which adds another challenge. I've participated and worked to help out on this forum for three and a half years, and generally redo recoveries are somewhat slower, and because of that, a surprising and frustrating situation for the person doing the healing.
The walking will help the shoulder pain. I suspect the chest pain is straight-up post surgical pain, and that will subside as you heal.
Good luck with your recovery! Glad you've joined us. One of our moderators, Bill, has had 3 Nissens, and I expect he'll respond to your post soon.
Words of wisdom by Eckhart Tolle:
"Whatever you fight, you strengthen, and what you resist, persists.”
“Worry pretends to be necessary but serves no useful purpose”
“Accept - then act. Whatever the present moment contains, accept it as if you had chosen it. Always work with it, not against it.”