In your shoes would try talking to his counselors and my own. Your discomfort about his coming home doesn't seem like a good reason to seek a half-way house for him, even though I know the prospect of having to deal with this alone is really scary.
In the longer term would you consider looking around at residential schools for him? It seems like he's isolated and...what little I know of Central PA teen rural life leaves a lot to be desired. (Or maybe life is the same everywhere these days...)