My B is very light-footed, agile, and careful with her steps… but every now and then, when she takes a spill (jumping up onto the couch, or jumping out of the car) it's like all feet fly in four different directions all at once and she splats hard. It sounds worse than it actually is... she picks herself right back up moments later.
Your pup could just be bumping into things because it sounds like he's got a lot of energy and is getting used to his environment.
You sound absolutely smitten, and he IS a cutie. But I agree that holding a little back until you're sure nobody else is looking for him is a good idea. Aside from vets and local shelters, you should probably scan Craigslist as well and put up a found notice for him (don't need to include pictures, but maybe a vague description so that the owner could have a chance to identify him).
He looks a little like a suspected basenji mix at a shelter that was posted to the BRAT message lists recently... also in Texas (San Antonio). If there is nobody else to claim him, I know you'll be ready to open your heart and give all your love to this guy so that he doesn't have to end up in the shelter.