In regards to speed... You need him to be more responsive to your 'go faster' cue. I had to do the same with my boy when I got him, he was lazy as! I worked on the 'ask, tell, make' idea. I would first ask for a faster canter by gentle leg pressure and clicking at him. If he didn't respond, I would raise the strength of the cue to a stronger cue from the legs, a big push from the seat, and clicking. If he still would move his butt, I would flick the reins from side to side on his neck, to make a noise, growl at hime and do the other cues. Eventually they learn that if they obey the first gentle cue, they avoid the harsher cues.