Bad news: Spots in the Air Force Marathon are sold out. Good news: They”re not ALL sold out, and you can actually still snag some. Even better news: You might be able to write off the cost of the entry from your income tax! (I’m not a CPA, folks, so don’t take that last part as gospel.) The folks at the Air Force Enlisted Village have a handful of tickets to the full- and half-marathon, and you can still register if you raise at least $500 for the charity. They suggest you ask 20 people to donate $1 per mile,…