The posts above mine have already covered a lot of things that I would have said. He needs to be taking you more, and needs to be connected. You clearly feel that he’s behind your leg; you can see that in how hard you’re working to try to get him to move forward, but in doing so, you’ve completely thrown away any contact that you have with him. Getting that responsiveness and that proper connection comes from flatwork, not from jumping more jumps. I agree with other posters that you shouldn’t be jumping without a trainer (personally I don’t think most people should).
With a horse like this, I’d do lots and lots of transitions - and he looks pretty dead to your leg, so I’d probably carry a dressage whip. Expect a response right away when you use your leg. If you don’t get it, flick him with the dressage whip so that you get an overreaction, and pair that with a double cluck so he associates that sound with having to go forward. You can do dozens of transitions in every gait. He needs to be prompt every time you ask. I’m currently training this into a pony and you have to be consistent for it to really stick. You also need to keep a steady contact with his mouth - that’s your line of communication, and when you throw it away like you’re doing in the video, then when you do take a feel, it’s like you’re yelling into the telephone right when he picks up.
Most horses wouldn’t have taken the distance you thought you wanted in that video where he stopped. He didn’t have enough impulsion to be able to do that. This isn’t a matter of “letting him figure it out,” it’s learning how to set both of you up for success. You can’t expect him to do the impossible and leave long with no canter. My trainer had a great way of teaching people how to let the jump happen and I’ll post it below (copied from another post), but know that there should a lot of flatwork in your future first!
A lot of people get so hung up on there being one perfect distance, and it causes a problem because they’re trying to aim for this one take-off spot at every fence. That puts a lot of pressure on you as the rider, and for some people, if they come off the turn and don’t see that one spot, they freeze, take their leg off, pull to try to make it happen, etc. Then if it doesn’t work out, there’s this negative feedback loop in your head of “oh, I didn’t get to the perfect distance, I’m not accurate, I’m not good enough,” and that can wreck your self-confidence. In actuality, there’s a range of distances that you can leave from, with the width of that range dependent on the horse’s scope. My trainer growing up had a great way of showing people this in lessons, but I can’t really do that here so please be patient with some poorly drawn stick art.
Let’s say the end of the ring is the bottom of the screen.
|===============| <- this is your jump
>>>>>>>x <-- hypothetical perfect distance (> just so your hypothetical distance is in the center)
So this is a lot of pressure on a rider to come off the turn and approach a fence aiming for this one little x. And what happens if you don’t get to that x? What if you’re a little long or a little deep? If you’re thinking about it as needing the perfect distance, that’s a lot riding on getting right to X marks the spot. But what it’s actually like is more like below:
There’s really a range for your horse, and he can jump from anywhere within here and clear it.
So what’s really key to getting from one side to the other? It’s not the perfect distance, it’s getting to a place within the horse’s range with enough impulsion and enough balance that you can be a little long or a little deep and still be okay. Getting to within that range can be summed up in 4 steps:
1.) Establishing a canter that has enough impulsion that you have options at the jump. I’m not talking about going fast, but about having enough canter that if you’re a little long or a little deep, your horse can still get from one side to the other.
2.) Establishing a track to the fence. It’s important to be straight. It’s really tough to find a distance you trust when your horse’s front end and back end are on 2 different tracks.
3.) Maintaining your pace and track to the fence. Once you come off the turn, you shouldn’t need to make big adjustments in stride or straightness (which isn’t to say there’s no adjusting going on, but you shouldn’t feel like you need to gun for a big distance or choke the horse down to nothing if it’s going to be deep).
4.) Jumping the jump 
I’d bet money that when you’re jumping around and it’s going well, you’re not getting to the same exact distance every single time, but you’re carrying enough impulsion and balance that you’re somewhere within this range and you’re confident that it’ll work. Your confidence gives the horse confidence. You know your horse best - maybe he really doesn’t like to get deep, so your range is a little smaller, or you need to support with your leg more at that spot, or maybe he’s weird and if you’re getting deep, you need to drop the contact - you and your trainer know his idiosyncrasies and your skill level.
It’ll be okay, OP! Just put in the work on the flat before thinking about jumping bigger jumps
