Very sorry to hear of your boy's trials. It's an awful, terrifying condition for both bengal boy and owner. There were tears, but the plucky kid took it bravely.
In our case with poor 11 month old Satai his back legs and tail were completely paralyzed, but he made a complete recovery and belts around the house chasing his burmese brother with alarming speed
.
5 months later he's still fine (and we're naturally desperate for this to continue into old age!)
The neurologist prescribed liquid Prednisolone.
The dosage was 0.8ml twice daily for 2 weeks (I guess that's 4mg), then 0.8ml once daily for 2 weeks, then finally 0.8ml once every SECOND day. So the total regimen took 6 weeks. It was the neurologist's view that this dosage was relatively light at the time, and he was prepared to crank it up if it wasn't providing the goods (He didn't have to)
My wife and I mixed it with some catfood paste, and hand fed it to him on a tiny spatula. Naturally this NOW means that the spoilt brat now gets this every night (sans prednisolone)
As for his weight I'm not sure (his jabs are due next week!): 3 kilos perhaps - he lost a startling amount of muscle mass very quickly and it took some months to regain.
The immunosuppressive behaviour of prednisolone was a concern (we were warned to keep him indoors, and hold off on innoculations as they might react badly, for example), and cortisone/corticosteroid is nasty stuff to take long-term.
Naturally I do not presume to provide vet advice for your boy (who could well be an entirely different situation): I'm a computer engineer not a Vet. I have, however detailed our experience as you have asked.
I wish you all the best, and really hope you have a successful outcome.
Our boy:) (taken after his recovery)