First of all, welcome and Merry Christmas! It's great that you and your family are supporting your brother.
Outpatient can be an amazing tool for helping addicts to recover. However, in my personal experience, (and this is just my experience, I'm not a doctor) your brother may need to be detoxed first. While opiate withdrawal is not fatal (you may feel like you want to die, but you won't), withdrawal from benzodiazepines (Klonopin, Valium) can often prove deadly. Long time benzo users can suffer from seizures, hallucinations, heart palpitations, and feelings of being shocked with electricity.
You mention that he has done nothing for the past two days, which is great. I would just keep a close eye on him to make sure he doesn't become delirious. If you notice any sudden behavior changes, I would take him to the emergency room ASAP.
Let us know what happens at the doctors, and again welcome!