I think you have it right.
This was an addict looking for an easy score who got scared off, maybe by some boisterous burly guy leaving the party across the street. A gun is always a good find, since a gun that may be on paper to another owner has considerable street value to some released felons.
The identity theft or code theft angles seem a little far-fetched.
If anyone wanted to obtain enough personal information to obtain credit in another's name, there are easier ways to do it than to break into a vehicle in the hopes that you'd find enough information. There are also safer and easier places to do a break-in than someone's driveway. Mall parking lots and especially parking garages come to mind. Yeah, they have cameras but the video is typically of such low quality that you can't ID anyone and one can easily escape visual ID by wearing a billed cap pulled low so that one's face is shadowed. Even if there's a good shot of the perp's face, unless someone who happens to know him IDs him, that picture is of little value.
The code theft thing is a little silly. It isn't that hard to lift an unlocked garage door against the opener. Try it yourself just to see.