Huge hugs to you. If she were my daughter, I would really want to get an IgG allergy panel done. There can be IgG allergies that affect the gut, but they don't necessarily show the outward signs of allergies.
Hugs to you again. Do you still have her off of gluten completely? One tiny exposure can cause the symptoms to all come back and she has to be completely clear of gluten for 3-6 weeks to see the complete difference. I know you have tried so hard, but that belly still looks like a gluten problem to me.
Also - How did the egg experiment go? I agree that it is worth a shot to see if she could get her fill that way. I also like the suggestion that someone else had about getting some of those oral sensory toys. Maybe she's not hungry. Maybe she just needs something in her mouth all the time.
Hugs again. I know how hard this has been for you.