You've gotten good advice and I agree with it. An ad is merely a come on, designed to make the reader want to know more. You don't want an entire history or story in the ad because then the buyer will make their mind up right then, and generally that means they'll pass.
What I see when I read your ad is this: 9 yo OTTB with negligible training (90 days), too hot for trail and nobody at this family does anything the horse might be suited for. He's a project with lots of energy. SO! If he was priced $750 OBO for the right home, I might slow down long enough to call or e-mail about him. At $1000, nope, skip, pass, not worth it. Being honest with you, horses like him sell for $500 all day long around here from private parties. At auction $200 or thereabouts.