I believe broom style should have a spreading nebari but this is certainly not traditional broom. Traditional broom is the deciduous formal upright so has a straight and vertical trunk. In recent years we have been seeing a new style emerge that some call informal broom and others have dubbed 'natural' style.
I think the trunk has character and the overall style is fine but maybe those branches are too long with little taper for the short trunk. In my experience, overlong branches are common when we try to achieve a result too quickly. More frequent pruning lower may take longer but gives a far better result in the end.