Shiraz is right on, the grid is your friend, the grid is god, the grid is all knowing.... You get the idea. Without the grid, making anything modular is going to be damn near impossible to keep clean.
Try make the wall on a grid so you can use the snap tool to evenly align the wall segments, also remove the back and sides of the wall to cut down on Tris as i don't think they are really necessary. I also think you can get away with cutting down on alot of tris let the normal do most of the work not geometry unless of…