For $400,000 you can get yourself a very nice house & piece of property in Williamsburg County, but as I am sure you have noticed, you will be in the middle of nowhere.
I am not very familiar with the schools in Williamsburg, but when I cannot think of any that jump out at me as being exceptional.
Manning (25 minutes from Kingstree) is a decent town in Clarendon County, but not sure about the schools there. They have a super Walmart, if that is any consolation.
Monks Corner (45 minutes) is a nice town, as well... you could get a nice spot along the lake.
Georgetown (50 minutes)has a very nice historic district where you can get a decent house in your price range. It has a nice downtown district along the Riverwalk. You would be 15 minutes to the beach. There is a super Walmart on the outside of town, too. It is a mill town as well. The paper mill lets off a sulfer smell that can be strong if the wind is blowing the wrong way, but folks tell me that they get used to it.
There are a couple of good schools in Georgetown but be very careful because there some bad ones, too. The McDonald School was awarded the Palmetto's Finest award for elementary schools.
If he is willing to travel just over an hour I would look at the Pawleys Island area or the Conway area.
I know this is not what you wanted to hear, but I hope it helps.