He is hopping because he isn't doing what he needs to do.
A) His hip is popping up and out of the ground
B) He doesn't have established bend
C) He is dropping his shoulder as his hip pops up.
In theory your pocket size is good and you are getting a turn in at a decent size, however he is being slowed down by not using his body.
While you are going slow, trot up to the barrel, stop at your rate point, push his hip in, and walk around it a couple circles. While you are walking this circle, bend him as if you want to drag his nose on top of the barrel. Overbend, because when he runs he will stiffen up. Stay nice and quiet, soften him gently, and then on the backside ask him to pick up the trot again and set a straight line towards your next barrel. Here it is important to switch your bend halfway so he knows to change leads, but the idea is the same. Come to the barrel, stop, push the hip, bend and go several circles before asking for an increase in speed on the backside to get him powering out.
Also I like to push their hip in while we are on the straight too, but remember never to lose that bend, and keep him soft. I notice softening is one of the things you have struggled to get out of him in previous videos I have seen of you. This time though he isn't bracing so much.
This exercise should get you started. I would also do a lot of counter flex circles off the pattern at the walk and really just ask him to be soft. I suspect he is going to brace against you on this but just bump your outside hand and ask him to put his chin down. Outside hand is a huge key to softening and keeping a horse balanced. Often I will say "inside, outside" to someone I'm helping, which essentially is just "inside" rein for bend, "outside" to stand them up and keep them from falling in, and of course using your feet to drive drive DRIVE their hind end up.
In a snaffle you could get him walking slow, deliberate, soft, and hold contact with your hands and squeeze with your legs until you feel him stepping under himself. Getting a video too will help you see that. After the walk a strong posting trot with the same thing, asking for a reach and drive from behind, and finally as the lope. The leg and contact will encourage his front end to lift which will encourage his hind end to engage.
Little things on and off the pattern will help you, and that should get you going on the right path for now. If I can I will try and get a video of Selena doing these things, as she is a good example of a bendy, soft horse just in general. Like Beau said too, Martha is an extremely bendy horse and will show you what to aim for, however not every horse will follow that style.
Hope this helps.
Pssh.I didn't pick up the wrong lead
It's called a counter canter...
...A very advanced maneuver.