My advice would be to have this discussion with your boss, but ask more questions and don’t complain so much. State the facts of the situation and minimize the feelings. Here is what I would do:
Schedule an hour with him, over lunch if possible. Let him know that you had difficulty with the project due to competing demands on your time, and trouble with the new direction of starting with existing tooling. Tell him you were really impressed with the evolution of the concept the freelancer did (see how I positioned that) and you want to learn how to move your concepts further faster. Next ask him his advice. How would you recommend I do it differently next time? What do you think I can work on to improve? When you were a junior designer were you ever in a similar situation? How can I prioritize my time better?
Engage him as a mentor not a manager and see if that shifts the relationship. Next time, when this kind of thing is happening, don’t let it get this far. If something is starting to go off the rails, ask your boss if you can set up a collaborative project workshop with him where you are both working on the solution together vs jest reviewing and not getting on the same page. Mush of these kinds of things are due to communication and alignment. We can’t read minds, so we have to collaborate and build upon each other’s thoughts.