The hand-thing is called syndactyly; it's the opposite of polydactyly. It's genetic in nature, and my Lefty has it, too. Humans can have it as well. Messybeast is down, but there's a good IVIS article and some human stuff you can search up. Messybeast has pics, but your baby has a pretty classic case. The split sternum concerns me most, and I'm anxious to see what turns up on the xray.
(Yes, Jan, it's me!!) Jan's been after me a long time to go ahead and join. :)