In the video, Good staying up and clam and not making it a bigger deal for him, kuddos to you for that but you need him alo and I MEAN ALOT more forward off your leg then that itty bitty western trot....Your arms are so low, so tight that you need to shorten your reins, spread them wide and bend at the elbow, I think a good short reins (NOT TIGHT, but have contact) would really help, having hands in your lap will just get you dump all the faster, but you satyed on, stuck with it and go through it!!! Good job. You need to shorten those stirrups of yours more, drive him from you seat, use lots of voice with him, it may sound dumb but he looks like he doesnthave any confidance in himself and you need to be there to support him, push him ad praise him for the good, doesnt mean pat him but "good man, Iknew you could, that's IT. You can do it.." with things like that get there attention you, not to play tricks to try to get out of it. If you feel him start to duckout, trying to turn off the other way growl at him, kick and spread your hands wide. Make him go forward even if its not to a jump but anywhere forward, once he is going forward relaxe, breath praise and act like nothing happend and go again. Forgive but don't forget, be on your toes (not litterally) and look ahead of where you are going, pretend there is no jump. Those jumps are so small that if you had gotten him ina forward trota nd looked up he mostly likely would have trotted over most those. You need more hip angle over the jump even if its this mall, its part of the begginings of your relase, once that's there move your arms up his neck, hands on either side. Getting your body to do this might be tricky. He seems like a fun horse but has alot to teach you and that's great! You will grow together so much in the next few years if you keep up like this.
If I where you I would work on" Getting your stirrups shorter, shoulers back, arms bent, hands wide and on either side of his neck and start working on praise and growling and sitting very deep if he starts to feels like he will drop out through either shoulder, if he does this and your going the other way like inyour video you kick him forward and ride him where you want to go with a purpose and all the time he starts going the way you want him to use your voice, "good boy" Think forward forward forward!!!! That's the first step to getting him to think about you and what you want, him going that's low gave him all the time to say oh here where are going this way now...nope this way...nope. I have been there done that its frustrating but teaches you to sit up, drive and move on like it didnt happen but expect every time. You will get there. Your pony is very cute!!!! Id snatch him up ina heart beat! You fit him well and I see you can improve alot with hime and patiance. ANotehr thing is when he throws his head down and around as if to say Im going to try to dump you be scared...having a short rein will make your arms bend more and hands up and that with should help with that probmelm, but again he does somthing naughty like that and I think its cause he has low confindace is growl say Get up there. Then as soon as he does breath and praise, good boy! And ride him FORWARD! I belive in you and know you will get there! Nice weather is upon us so get out there and practice practice practice!