It's really late for acceptance to college. At this point any interested D3 would tell your son, sure walk on. It's a crap shoot. The coach has already recruited the six to eight studs he was looking for.
You might want to consider club baseball at Texas A&M. Club teams don't travel as far as varsity programs. Homework and grades is more of a priority than baseball. At a school like Texas A&M the team might be a bunch of players who tried to walk on or washed out of the program and didn't transfer. In other words, reasonably talented.