Horseycloe, sorry for sounding rude. I don't know you so I'm in no position to judge you, but personally I don't support young riders like yourself who are uneducated with young ponies. I've seen far too many accidents. And personally I didn't like the way you rode in the video.
I think that if you listen to the advice on here from JDI, WS etc they might help you solve your problems. But I would also seek out the help of a trainer because it just sounds like you're not qualified enough to deal with a rearer.
I do want to have more lessons (especially on Spider) but I can't get a hold of my coach. She is a EFA approved dressage coach and has taught me soooo much! But I just can't get a hold of her. We've rung numerous times, her phone must be broken I'm not sure. And I can understand ur worries for me. I am a bit young for a rearing horse, but at least I can control him. So don't worry, if he starts to make rearing a BIG habit, then I will contact a trainer to get the rearing out of him
Thanks for all ur help everyone!