I've been through what you're going through and my dragon did survive, what I added to the mix was this: Carnivore Care, bee pollen and Acidophiluz+ This all helped and after a year of eating all this, Sweetie started eating crickets and greens again & regained all her strength.
I would also recommend a
bath daily, to help with rehydration. Electrolytes would also help, even with a weekly
bath, it's easy for a dragon to get very dehydrated when brumating. I get my liquids at Tracie's site
www.bug-de-lite.com I've found the Acidophuliz (a good probiotic liquid for beardies) and electrolytes helped my beardies get their energy back after this long winter. I have 5 adult beardie males and an 8 mo old male, too, who's just new to me, have been raising rescued dragons for 7 years and have gotten a lot of advice from other people who rescue, as well as Tracie & other moderators here.
I wish there was a way to find out why some dragons get so sick after brumation and others don't have a problem. Rubio, my 5 yr old, brumated for over 2 months and it took over a month of giving him all of the above with calcium, vit/min & babyfood for him to get back to normal, even then it wasn't until 2 weeks ago that he was fully recovered.
I so feel for you, and I'm hoping that your boy recovers on his own with the good care you're giving him. I also wanted to add, that flipping over isn't good for them, but they don't necessarily die from it. I have a 10 year old dragon, Lonzo, who flipped over a lot a year ago, he has arthritis in his back and that's caused his tail to sort of wag, it also caused him to flip over. He survived all this but his right lung ceased to function. A year later, he's still getting around, having only 1 lung to breathe through isn't stopping him from enjoying life. Though back last year, I was so afraid I would lose him.
So good luck, hopefully this helps some,
Deb