It's a bit of a long story. TL;DR at the bottom
I am in a martial arts club for ~10 years. My trainer is not a friend of Japanese dojo style but he made the training more open and like a workshop, which was appealing to me. Over the course of the years we became friends and we did some projects where I helped him in various situations.
He was often seen as kind of strange to other people, e.g., he would hold unconventional viewpoints and cared little for the reaction of others to said point, or he would phrase things in a provocative way and say that it is not his problem if people react to his provocations. At first this all happened within certain limits. You could argue in favor or against his viewpoint but it was not vastly disturbing.
Over the years this changed. He always had quite a strong self-esteem but he began to exaggerate. He'd make mistakes and not deal with them. Then he began to shift the blame to others. Over the last 5 years he gradually became a person that is completely unable to take critique and is not able to admit mistakes whilst always blaming you for something you did.
As stated before we did some projects together. We managed to make a bit of money through these projects and he would always promise me to give me a share. This was fair as I invested a good amount of time and some money.
However I never got any money or anything else. He'd say that he was waiting for the money himself. He'd say that he has it but that it's only part and he'd give me my share when he got the full sum. He'd say he hadn't calculated how much I should get and that I should give him a list of hours I worked on a certain project. I gave it to him and he wanted some clarifications. I added them, then he said that I should talk to another member of the club because she had a different view on the project, and so on... As soon as I delivered something he wanted he came up with the next issue. I completely understand if you want to do things correctly but if you always come bit by bit and start bringing up things that were not mentioned when he first requested the list, it is irritating.
A few months ago (this went for more than a year) I stopped yielding to his requests. I'd say that he has every bit of information he needed and that after over 5 years I at least want money for the things that were clear.
He began to accuse me of being sloppy and brought up some mistakes I made. I did make the mistakes he stated but they all were minor, like twice I was not able to make it to training and I called him only two hours before. Nothing major, nothing loss incurring.
Whenever he wrote me, his messages were full of accusations. Whenever I tried to disprove or question them, he came up with more. He'd accuse me of not being constructive, that I waste his time, that I am not a grown up but more of a child (I'm 29 btw). Even when I present him facts he simply glosses over them. I have the feeling that he doesn't even read my messages. He simply picks some points I make, twists them and accuses me of attacking him, e.g. I told him that he could buy a pool for his garden (privately) and quite buying expensive equipment for the club whilst I was waiting for his payments and that he at least could have paid 50 bucks a month. He answered that it is none of my business what he buys privately, that the equipment was for the club where I am too and that I should mind my own mistakes I made.
TL;DR and question
A friend of mine is refusing to compensate me for projects we did together and when I try to talk to him about it he constantly blames and belittles me. He is completely immune to arguments based on facts and uses every little thing I did wrong as an excuse to delay all payments.
How can I deal with such a person? I simply want to clear things up and make a clean cut, as the events of the last year have shattered my trust in him and his club. I fear that my investment into our projects is lost as I trusted him and we made most agreements personally, not in writing.
I'm not a psychologist but he shows many symptoms of Narcissistic personality disorder such as over exaggerating his own successes whilst always criticizing his surroundings. Does someone have experience on dealing with such person?