I don't want to scare you and I'm not promoting the products used in this article but I think you should read it. It explains about the scabies.
DERMISIL.COM :: How Fast does Dermisil Work? ::
Your little one is so small that you really need to help him keep his weight on and immunity up.
Do you have any NutriCal?
Nutri-Cal
If he won't eat his normal food - try boiled chicken.
Feed him frequently - every 2-3 hrs.
Keep his bedding clean.
Give him lots of love!
I hope this helps for right now - check back often because I'm sure more people will be coming on to help you out.