As he was not seen driving and there is no way of knowing how the crash happened he can not be charged with any driving offence or with D D . As he later did admit to driving he may very well get away with leaving the scene of an accident as well. Same applies to the theft report ,the police will probably not pursue it as he will just say he was scared and did the wrong thing in the heat of the moment.
To sum up he will almost certainly get away scot free apart from an insurance claim and as that will be met by the company that will not effect him anyway.
In reality he was probably p*ssed and this is the way of getting off the DD charge. I know a man who did the exact same when he was drunk , got away with it all apart from an insurance claim.
Not what you want to hear but I think he will get away with it totally, this is a well know method of getting off drink driving when you have crashed the car. You report it stolen so that you can not be breathalysed until you have sobered up , then 'come clean' and say it was due to being scared , as nothing can be proved there can be no charges.