He sounds to me like a reining horse with an english rider. The reason that I say that is because he responded to your kissing noise.
If he was truly used for reining, he knows how to engage his hind end. A reining horse is nothing unless they're working off their haunches.
I would attempt to collect him in, make him work real hard at a jog practically in place. Then push him out and ask for a lope.
Another trick may be barrels. It perks up my guy (trained in WP and reining) for whatever reason. I set up a barrel pattern and run it totally out of position making him gallop on 'home'. Then I put him on the rail and he's a charm. Go figure.
It sounds to me that he needs something to engage his mind, and once you have that (whatever it may be) I think you'll be set.
Also- if you're sitting to hard and too deep, he may have been trained to slow down. On my horse, if I squeeze my lower leg at a jog, he's to slow it down and collect up a bit. Same at a lope, the tighter my legs and deeper my seat, the slower he goes. I know that if a rider who I hadn't advised just hopped up on him, he wouldn't do much for them squeezing forward.
Find out exactly what his cues were while doing reining. My guess is that he was taught completely opposite cues.
Good luck! Keep us posted!