Hello, my name is ***** ***** I look forward to assisting you today. I bring nearly 20 years of experience in various legal disciplines, including JAG.
Getting a discharge
upgraded is an exceedingly difficult thing to do and that's just moving it to a General discharge. Moving from OTH to Honorable won't happen. They are not automatic, and in fact, are not contemplated as a normal or natural occurrence after a certain period of time.
There are only two ways to do so and both have the same burden on the person making the request. You can file a DD Form 293 or a DD Form 149 (though this one technically has a three year window following knowledge of the issue that you are filing about...it is often waived, but not always).
Before either board, he'd have to prove that the discharge he received was an injustice at the time that it was given or that the discharge was an error.
Regrettably, on just the facts you've outlined here, he wouldn't be able to meet either standard. An OTH is a legally available discharge status for an AWOL situation, so it's not an error (unless the board actually said that he should get a different discharge).
It's also not an injustice because an even lower discharge status is available for that offense.
There would need to be some other mitigating facts which should have been taken into consideration but unfairly weren't for him to have any sort of argument for an upgrade on these facts.
As for a federal job, that's unlikely with any discharge lower than an Honorable. While it's not a complete bar, it is absolutely something that is considered for all federal service and an OTH is going to be prohibitive. A general would as well, though not as dramatic as an OTH.