From the first video, I think you need to release a little bit more. Your hands, to me, look like they're in the same place before the jump as they are over the jump. As the jumps get bigger, your horse will rely on his neck more, so just remember to be generous with your rein.
I have the same problem.
Second video, I noticed that you stiffen up a few strides out before your horse jumps. Relax! Easier said than done, I know. But you look TONS better than in your video in the other thread! You make progress fast!