Dave Boyt
ArboristSite Guru
3" from the wall results in dead air space, so the fan will help, but you need it up to move the air evenly through the stack. Might use a couple of fans-- one between each column of stickers. Fortunately, walnut is the most forgiving wood there is, when it comes to drying. I think you'll be fine. You might see a little end checking (cracking). Some people put latex paint on the ends of boards to reduce this. Give it at least a year.