Please help my python and me fix this mess-

my ball python has been got a very sick looking tummy - it must be scale rot or infection or something else? (please can someone tell me how to attach pics? can't see link here?) i can see some oedema and swelling, his whole underside is brown with blackened scale tips. He's also apparantly been off his food for a couple of months (which i was unaware of) - can malnutrition add to this or be a cause of this? will he survive? (he seems normal in activity and character so perhaps there's hope he can fight this)

he's going straight to the vet tomorrow for advice and i guess antibiotics- is there anything else i can do? i have read on betadine washes but wanted to check first on wether this is a good idea and on how to apply/how dilute- i don't want to causea any pain or make it any worse. I have cleaned the cage thoroughly and its dry other than his water bowl.

OK and please don't blast me for this I have been crying about this all morning and am fuming this has happened i've had him for 3 years and he's been happy and in perfect health and condition -I no there is no excuse for this but before you judge my pet has been with someone for a few months who was supposed to know about basic care for pythons - i will NEVER leave him with anyone ever again.