Such a sad story...Im sorry for your loss.
I had a Japanese bantam girl with almost the exact same injury except it also went down her back. She looked like a package of chicken from the grocery store and was in serious shock and the like...
I flushed her wounds with saline and put bactine all over her, and I spent hours sewing her up with thin plastic thread...The hardest part was that there was much muck and dirt inside her skin and I was afraid for infection from that.
I just flushed and sewed and flushed and sewed until she was completely closed up...injected her with some Tylan 50 and put her in a warm hospital tank...and by morning when I cane down, she was perched on the side of the tank!
It took her a long time to get better but now, a year or so later, she is out there running aorund with her kids and she is none the worse for wear except for some missing feathers along the huge scar that wraps across her head, down her neck and then down her back.
She is a strong and serious little bird and she perches in the main barn with the big hens and roos...no bantam barn for her!!
I just wanted you all to know that if this happens to you, its probably best, if you catch it right away, to flush alot, bactine for pain and antiseptic, and sew it up with plastic thread.
and injectable antibiotics are preferable in my experience....
again...sounds like your girl had great care and she tried hard....those respiratory things look for the stress and weakened birds...
Ive had problems in my flock with respiratory and in many ways, Id prefer to deal with something straightforward like a skinned bird, than all of these terrible CRD mycoplasmas and such!