Builder,
It would be awesome if your able to upgrade your return trip to first or business class. Take it from someone who traveled out of state to have surgery twice. The first time I did the coach route and my return trip was pretty uncomfortable... yes I managed but... And the second trip I did do the first class route, that extra room just made all the difference in the world.
Mind you it wasn't for back/neck surgery but thoracic outlet repair. And the flights were only from California to and from Colorado not like your international flights.
I DO understand the cost factor though, amazing the difference between a few inches of seating and leg room isn't it?
Ohh, and I also found out that if you let the airlines know you are medically "fragile" they will greet you at the gate usually with a golf cart for transportation through the airport. Something that might be very helpful for you, especially post op.