Good Luck!
I think you will (if he stays for full treatment) have more than 28 days, if he blew .6 wow, that is coma/death BAC. and that was when his Dad got there and he kept drinking, so it got higher and higher (even when he stopped drinking) So, I am thinking he would need to stay in the hospital for at least a week before they let him into the actual rehab treatment center.
Your post didn't indicate that, but there are very few rehabs that allow someone to come in that isn't sober/clean for at least 72 hours since they don't have the resources to deal with DT's etc.
If they took him and do not have the facilities, do not be surprised if he gets transferred within the next 24 hours to the ER.