I do like your idea for a twin trunk design and I think the movement you wired into the smaller trunk is very pleasent. However there are two major issues that need to be addressed that I see in this tree at this moment.
The first is, your main trunk and your sub trunk and moving in opposite directions. This creates a scattered unharmonius image, the viewer’s eye will be confused because it will be pulled in two opposite directions. Look up some photos of twin trunk style bonsai, you will see that having both trunks move in the same direction is paramount to making the composition work well. You can still accomplish this.
The second issue, as @DavidJ mentions is that once you get above the first set of branches the trunk remains quite straight and taperless and boring.
You didn’t screw it up, there’s still a lot of potential for a great design with this tree. Here are my suggestions:
Yes… I would draw colorful lines all over your tree!
. No, let me explain… I would chop the trunk at the red line and then use the first branch on the left (underlined in green) as the new leader. The green arrow denotes the direction I would bend this branch to become the new leader and trunk line. Bend it up and to the right so that it mirrors the movement and direction of your sub trunk.
Circled in blue I see at least two branches were cut off here, one of these could have made for a better leader, possibly. You can’t glue them back on, but I am always very hesitant to remove any of the lower branches on a tree like this until I know exactly what my design plan is. A learning moment perhaps.
The other branch coming out the back below the red line could serve as the first branch for the tree.
Now, in terms of the work that would need to be done and the time frame of when to do it… I would not do any of this right now. The only thing I suggest you do is to wire that “new leader” branch upwards instead of to the side so that it gains more viguor over the next year.
Since it looks like you’ve done a fair amount of pruning, don’t make the chop until next fall probably. In the spring, pinch all of the candles above the red line quite hard and do not pinch the candles below the red line at all. This will help transfer more vigour to those lower branches and get them ready to support the tree for when you do make the chop.
Anyways, just my 2 cents!