Hi red cat,Welcome to the Healing Well 
Wrapped Club! I think you're our first friend from Scotland. Very nice to meet you.
At Day 9 you're moving toward peak swelling, so yes, you could get some reflux simply because the wrap can be misshappen when it's swollen, so a bit of reflux can squeeze through.
Also, you could be getting some food/drink held back by the wrap. If it sits in your esophagus it can be irritating, and can even feel like reflux.
You may have read here that the esophagus is a "dumb organ", and it can't differentiate among pain sources, so it interprets all pain as reflux. Some of what you're feeling could be normal surgical pain being interpreted by the brain as reflux.
I don't know if you already saw this in the Resources section, but here's my recovery journal for the first 19 days or so.
https://www.healingwell.com/community/default.aspx?f=45&m=2183443
I also had lung issues due to reflux, and it took two and a half months for me to feel improvement, and then it almost seemed to happen overnight.
I think you are very wise to stay on the PPIs while healing. People with LPR/atypical symptoms are much more sensitive to very little reflux, so it's even more important to be protected while you give your wrap a chance to heal.
Nausea is a common post-Nissen symptom. Have you asked your doctor for an anti-nausea script? I learned here the importance of having an anti-nausea med handy, just in case you get a virus or if your nausea is bad enough to make you feel like actually vomiting. You won't want to retch or vomit after this surgery. At your stage you could really do damage to your healing wrap. Even now I carry it with me wherever I go, just in case.
Remember that your stomach has been through a lot. It has been stretched, wrapped, and stitched. No wonder it's complaining. Be careful to eat foods that won't challenge it too much. It will take some time, but the nausea will pass. Until then, do whatever you need to do to help it feel better.
Again, glad you joined us!
Very best wishes,
Denise