You've gotten so much great advice here, I just wanted to offer you some hugs and support and GOOD thoughts that little Harley can get past his fear soon.
I agree that the little kid that kicked him is key here, Kelli had problems with children because she wasn't raised around them. We had a child that we babysat for a few times who would leave Kelli alone for the most part, but would sometimes chase her with her toys and Kel would run and try to get away from her and when THAT wouldn't work, she'd nip at her. Took several times for me to make the little girl understand that Kelli didn't play that way and she couldn't be aggressive with her. It's horrible to watch them be so scared/mean.
*hugs you* I hope that your trainer can help you and little Harley out.