I'm so very sorry to hear about Tweedle:hugs
You can do a necropsy yourself if you are up to it. I only seem to have one link that works at the moment that shows how to do a necropsy. @coach723 do you have links to any other necropsy manuals...
How long have you given the Monistat? I would go for 7 days.
https://www.backyardchickens.com/articles/how-to-treat-sour-crop-and-impacted-crop-and-how-to-know-which-one-youre-dealing-with.73607/
I've had that with crop problems, the "burping" and air. Just try to massage it a few times day...
Give him a direct drench of undiluted Corid Liquid for 3 days at .10ml per pound of weight. This is in addition to making the Corid water available to drink - use the mixed Corid water to keep him hydrated, so if you need to, syringe that into him.
If the Thiamine is in the food, that should...
Poor fella:hugs
You have had a rough time!
Can you tell us what antibiotic the vet gave you for the respiratory illness?
What wormer and the dosage that you used?
Anyway you can get a fecal float with the results coming back in today?
Crop problems can make them feel terrible, but if he were...