First, congratulations on getting through it all, and welcome to PPRuNe.
I have known several people who have worked at or studied at Jerez, including a (former?) Mod here. Some have had good experiences, some not so good.
It also came to my attention, when doing the written exams, that he had the power to pass or fail you, depending on whether he liked you are not.
No, he doesn't. You should get a debrief after taking an exam, and you can query ANYTHING. He cannot arbitrarily fail you. If you achieved the pass mark, you have passed. End of story.
If anyone had treated me the same way you describe him treating you, I would first have had a word with him quietly, then a similar word with him publicly, and then gone to his superior, and then left if nothing had changed at each step.