I personally think there is some paso in there. From the withers back he does resemble a paso the head Im not sure of. One thing though...pasos can trot and do quite requently until the muscle to gait is built up. My overall Judgement... he's pretty right? You like him right? He's comfortable to you right? Then he's perfect!
Check his feet. TN Walkers have clodhoppers for feet. Not a saddlebred and definitely NOT a Paso. A lot of TN Walkers don't trot and if they do, it's horrible (at least Spirit's is). Try and get a video of him gaiting.