The 2B is not bad...it is not as bad as an RE3.
But I would not bet on that being the case...that is, even if he waits, there is no guarantee that they will allow him in.
That is because he will need a waiver. All RE Codes other than RE1 require a waiver.
An RE2, as I mention, is not as bad as an RE3 or 4...but it still requires a waiver.
And they are TOUGH to get
The largest problem you face is the poor economy. The poor economy has caused a flock of people turning to the military for jobs. Despite the war recruiting is way up in all branches. The need for the services to grant waivers has decreased. For example the Marines
recently decreased their maximum age for enlistment. Its tough today to get a waiver. For anything. So it MAY be he waits and can get a waiver...but as I mention, it may be he waits and they deny the waiver request.
That leads to your question, should you request a change?
You can certainly try that route.
But understand that there is no guarantee for that either.
In fact, it is tough to get the record changed. He would have to show "error or injustice" in the record to get them to change it.
So, for example, if he could show that he did nothing wrong, and they made a mistake? Then the board of corrections could make the change. But what you describe that is not the case...it sounds like there was misconduct, and they separated for that reason. So I think you have a tough case for a change to the record. The only way they will change that RE Code is if you can prove the reason for separation is not valid...and to prove that you need evidence to show that he never committed misconduct
Sorry to have to bear bad news...but I do not think he will have success with a request to change that record (the re code)