Thanks for sharing your experience. I'm sorry to hear that you are dealing with this. What I'm hearing is that you need to at least slow down the production enough there so that the incision can start healing, and now that's not happening.
Do you need to wean cold turkey on that side? If so, be sure to express off enough periodically so that you don't become engorged or get plugged ducts or worse. Is is possible for you to do this somewhat gradually? There are a few ways you could do that - offer this breast after the first at each session, offer it for shorter periods of time, or for fewer sessions each day.
As far as relactating on that side, I would start with offering the breast and/or pumping, before you try introducing galactagogues. Presumably you will have a full supply on the right side while the left side heals. If so, you don't have a supply problem - which is what galactagogues are for - you just want to re-balance your supply between your 2 breasts. It may not be necessary to get up to a 50/50 split with the right and left sides, or it may happen gradually with a bit of time after you go back to 2 sides. I would just aim for at least *some* supply on the left side, so that you don't get up a creek if you have any challenges on the right side later on.
When women wean (on both sides), it takes many mums a lot of months before their breasts are totally dry. Its a hunch, but if you stop on that side for a few weeks (how long do you think it might take to help the incision start healing?), but are still nursing on the other side, its my guess that you'll still have some production on the left side, but hopefully it will slow down enough to let the incision heal. Just a hunch - production is independent between the 2 breasts, and stimulation and emptying the breast are the most important factors for supply. Are there other mamas who have nursed only on side who can share their experiences?
It is possible that your baby will develop a preference for the other side. Be patient with your baby, and if its a difficulty, try using some of the nursing strike techniques to get baby back to that breast - skin to skin contact, offering the breast when baby is sleepy or asleep, while in the bath, etc.
I hope this helps. You are one tough mama!