Sorry did you say the only thing driveing 200 yards was a dog.
Was your colt loose was well ? You must be very fit running beside him in canter longlineing.
I think you have lost us a little.
Long line him and handle him let it be fun and educational and feed him tit bits as well.
I will say this again he is young and needs to grow.
And like the other drivers have said he is still a baby as thay have said as well as me if your driveing him at that age problems in later life will occure.
Take it from me tammy was 34 years old when I lost her.
And my gilding tricky is nearley 28 years old and he will live to a ripe old age he was broken to harness at 3 years old that was long lineing in walk with him in harness ocasionley on a quiet blocked street and that was rewarded with titbits and in the shafts work time was limited to 15 minuits in walk in the shafts with me long lineing beside him giveing him comands and tit bits and all ways left the class educating him on a good note.
As a reward he had his play time.
I would not get him to jump as could make problens whilst in the shafts.
And jumping him could jar all his tendons and joints as well.
He needs to develop a lot more.