Lunaki, your situation stays on my mind so while I was pondering, an "ole timey" method of dealing with sour crop came to my mind. Someone on BYC board had mentioned it when I was struggling with this a year ago. I believe she told me at the time that an old farmer had told her about it and she had done it and it worked. I did it and it worked way back but when I tried it again as the sour crop returned several times, it didn't work. But, you can consider it. As they say, "it wouldn't hurt."
After you've removed as much of the crop contents as you can, inject 5cc of wine through your feeding tube and wait 3-4 hours, giving the hen no food or water during those hours. On the successful time for me, all of a sudden, my hen just spewed out a bunch of poop. She had not pooped a lot until then. From then on, things began moving through. I still kept her on the soft diet for 2 days before I began adding back in the crumbles.
The problem with my sweet little bird is that she cannot have ANY grass. I learned that the hard way. After the first round of dealing with this, she finally got back to her "family." About two weeks later, she began having the squishy crop again. We struggled through getting that cleared up and she returned again. Even though I was getting grass out of her, it still didn't occur to me that she could have NO grass. After I took her off any grass, she has done wonderfully well. When the others get a little "road trip," she has to stay home. She doesn't seem to mind in that she isn't fretting that she isn't with them. It appears that she's quite happy even when by herself. So, when you get your bird straightened around, consider keeping her off all grass. I'm sure you don't want to have to go through this again.
Now, back to the wine...I don't drink so I had no clue as to what to get. When I went to the grocery store, I couldn't believe all the choices! Guess I don't get out much.
Anyway, the cheapest kind is just fine. Do not give more than 5cc. And, don't use any water to get it all down the tube. I took off the syringe and blew gently to make sure it was all out of the tube.
It's just a thought. You may choose to ignore it and that's OK. I'm just trying to think of things to help.
I won't be home most of the afternoon but I'll check the board again this evening. I'm pulling for you and your hen.