Very hard to tell much due to the shaky camera and the distance. I can see that your leg is coming up and wonder if having a crop would work better? Or is he too nervous with that?
He is a youngun so one should not have unrealistic expectations. He does have nice rythm to the trot. The way he is pushing down into the bit , comeing behind the vertical and kind of plowing forward onto his forehand is something that you would not want to become a longterm habit.
If he wants to reach downward, I would give him more rein so that his head is on or in front of the vertical. If he starts plodding, put more leg on and he will leap forward, raising his whole neck and head where in you can then ask him to give a bit to the bit throught the poll without him overbending and tucking behind. When he starts doing this ovebending or coming behind the bit, open the rein, push him up and "catch" him while his head and neck are up. Gently, though, on the "catch".