Anxiety is very common with GERD. We see it all the time with folks that come to the forum for help. Since it can spiral out of control over time, it can be very devastating. It is a very good idea for your father to get counseling help in addition to the medical care he is receiving. There is a very strong mind-body connection, and his recovery will be much faster if he can overcome his anxiety.
Upper GI tract tissues take time to heal when they've been damaged by acid. It's not a quick fix. It will take a long time for things to heal, and if he can get help with his anxiety, it will definitely help a great deal.
He is lucky to have you as his advocate!
Very best wishes,
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.”