I've read the first page... and I'm going to give the answer I got from my father-in-law (who's a leader of several school committees).
First step: document, document, document. Gather all the complaints. Present them as facts, not as complaints. Make them as concrete as possible. (I know. Not easy.)
Eg.
Bad example: He's making life hell!
Good example: I asked him a question and he answered I that was lazy and would know the answer if I studied.
Go higher up. If the dean is not responsive, go to the vicerector - and document the actions of the dean.
Is there an "educational service" in your university? I don't know the right name in English - in Dutch it's Dienst Universitair Onderwijs - the ones responsible for the education and didactics. Go to these people, too.
Assistants can not change much by themselves. If they are willing to help, gather their testimonies too and add them to the list you're going to present to higher authority.
Students CAN do something. I will give you an example.
In our university, they wanted to throw Mechanics out of the Physics curriculum. Now, all the students love Mechanics - the professor is good, the subject is interesting and important to physics, the combination really helps you to understand physics.
They decided this during the summer break.
First thing we did was talking to the Mechanics professor. He was almost depressive - and we convinced him to not give up the fight.
Then, we (the students) stated that the decision is not valid, as there were no student representatives due to the exams. So a new meeting was called. We had the right to 5 student representatives. They asked me to be the fifth. A lot of professors were really surprised - students asking for MORE lessons!
And it worked. From then on, whenever the students asked for something, the good Mechanics professor voted in favour...
Edit: if you dare, let the word "press" fall somewhere. There is nothing so scary to a university as a bad reputation.