Jaxx - sorry to hear that your son is going through this. I wish that recruiters wouldn't "brush off" things like this. It would have been so much easier (but more work on the recruiters part) to have you address this BEFORE your son left for BC. He would have had to have gotten a waiver for it and yes, it would have taken more time, but now it's looked at as if information was "withheld" and that doesn't look good.
There is a good possibility he could be sent home and then he'll have additional waivers to get in order to re-enlist (I believe after 6 months) but it can be done. Let's hope it can be resolved while he is there, but don't be surprised if it's not.
Here's the link to the Ship 5 group - let's hope you don't need it but still take a look at some of the discussions there. You might find some helpful info - there's also info on re-enlistment codes. Keep us updated on the outcome.
Here's the link to the reenlistment eligibility chart codes - just to make it easier for you to find!