Hmm.......... Theoretically you can. But loads of factors have to be taken into account: how long has it been deleted, how many texts has said person received since, obtaining appropriate software and researching how to use it etc... It's not a simple task.
No. Even if it is his, I doubt the phone company are going to disclose it. Because it'd cost them a lot of time and money. Even under the data protection act (if Americans have similar) it might not be possible.