I'm so glad to hear that you're doing well! Welcome to the Wrapped Club! Bloating is a typical issue during healing, and I agree with your doctor--walking would really help. He set a pretty high bar...an hour a day! Why not just do whatever walking you can handle...start small and build as you feel like it.
I remember years ago when I had gotten out of the habit of walking. I was working full time (a second grade teacher) and I was exhausted when I got home. I always used that as my excuse. Finally I decided to just walk 15 minutes a day. I just pushed my tired body out the door and I walked. Once I'd done that for a while, it wasn't enough, and I added some time/distance. That continued until I was walking probably 45 to 50 minutes a day.
I totally get why an hour a day seems daunting. Try 15 minutes. It's better than nothing! Then see what happens. Just a suggestion!
As far as fizzy drinks go...many here who enjoy soda have let it go flat in the beginning...that way they can get the flavor and caffeine without the carbonation. You can try sipping the carbonated version, but with your description of bloating, I wouldn't recommend it. I think it was Joy who just sipped on her soda throughout the day. Some people are able to burp, and start on carbonated beverages right away. Everyone is different!
As far as your lungs/breathing issues go...I think you're right that it will take some time for your body to adjust to its new configuration. I had breathing issues different than yours (very severe asthma/lung infections) and it took two and a half months before I noticed improvement.
Again, it's great to hear you are doing so well!
Keep up the great work!