I'm sorry to hear that you're having so many problems. It's not easy, I know.
As to your question regarding stress and digestive problems, the answer is a resounding YES!
Here is just one URL that makes the connection. There are many others:
You still have some healing time. I continued to improve even after the year mark.
Have you considered seeing another surgeon as a second opinion? If you could find a surgeon who specializes in these surgeries and other similar ones, you could get a good idea about what's happening. You'd have to be retested...24hr PH monitor, endoscopy, manometry, barium swallow. With that information, a skilled surgeon will be able to determine if you wrap is intact.
My asthma doctor wanted to rule out reflux even though I'd had the Nissen in Feb. 2009. I went to the surgeon who "does all the Nissens" in the city where we recently moved. He put me through that battery of tests and declared my wrap intact and doing fine. I'm sure it would be helpful to get that information for yourself.
Getting a second opinion would give you a different perspective.
Try to relax. Stressing is only making things worse.