I love how people are reading the OP and not anything else, the questions being asked have otherwise been covered in his posts or have been asked before.
Anyways, here are some things that I thought of on this subject while making my coffee today...
1. Ask why you made the grades that you made. You mentioned that he asks for one thing and grades based on another. Record what he asked of you in some way, if he wrote it down then take a picture of the thing written down, if he said it via word then record it with a tape recorder. Then, if he grades you based on anything else, record that in the same fashion.
As a student, you have every right to understand, keyword understand, why you made the grade that you did. Present your recollection (memorize what he assigned verbatim, DO NOT TELL HIM YOU HAVE TANGIBLE EVIDENCE) of what the assignment was. If he says otherwise, have the tape recorder on to get this evidence. I did a price conversion (taking from the price of a tape recorder in America) and a tape recorder over there would cost ~15 European Dollars. If you don't want to pay for it, get some students to put in one Euro or a fraction of one to go towards your paying for it, since this would be to benefit the class. I'm assuming that you or a friend has a camera that you can use. If not, get one from a classmate, they will definitely understand your motive.
After doing this if he doesn't comply (I'm assuming you already have, but I was just throwing that out there), go to the dean and present your evidence. I would only do it after you had a good amount of evidence, one assignment wouldn't be enough.
2. Complain to your OTHER teachers. You mentioned getting close to your teachers to get better grades etc, so in a discussion talk about this teacher. If you haven't already talked about your other classes, just mention something that would make them curious about what other classes you have. "Oh this is just like what happened in another class of mine! How interesting." etc. Then they will ask you about what classes that you have, and from there you can explain what classes you have and that will lead to your tangent (that you have planned in your head) about this teacher. Do this with every professor, and get EVERY student of his to do it to their other professors. Another good thing would be to team up with one or more of your classmates against this professor when you are going on this tangent. A crowd has a more profound effect on a person.
A terrible teacher like this doesn't deserve the job. If I were a professor I'd honestly feel pressure, because these student's futures are in
my hands. He is just being destructive, and is a bad person for doing that (in my opinion). I don't care if a professor has a stressful life outside of school, what he's doing is pretty much unacceptable. He could at least explain that he has a hard life outside of this if he actually does. He could make changes and provide extra credit, he could actually grade things how he said he would. But no evidence of that has been presented, and it just seems like people are just trying to make you stop via guilt tripping lol. He is fucking up your future and hundreds of other people your age's futures, and you don't need to back down.
If NONE of this does anything, avoid him at all costs and tell everybody to never get a class with him. If your college has a web forum, post that anonymously if you can and give a warning. Give all of this evidence, and tell people to never take his classes because it will bring their GPA down.