Well said, and glad you are here
Many of my colleagues and their reservations about this echo my own. I will just try here to contribute as another voice.
First of all, it is wonderful that you are here and listening to the voices of several very intelligent tarot followers. It seems you are here to listen, so it would help to hear many voices.
I understand that you are portraying the abuse of tarot cards with this film and using special effects and horror to attract a large audience. I don't think this does anything to advance the cause of tarot or the misunderstanding of it, but, of course, that is not your goal. Your goal is to make a horror movie, a popular genre that attracts large, and primarily young, audiences. I am a teacher and, in addition to teaching at a regular public high school, I also teach an adult high school at night, with great freedom in my curriculum. One of my courses I designed is in the study of multicultural folk literature. In it, within the last two years, I have worked in a unit on the tarot. I already have a difficult time with devil worship misconceptions and "it will tell the future" misunderstandings. Should your film become popular, I have no doubt that further misunderstanding will result.
I see your argument, and in fact I have seen it used by many rappers in defense of the violence and misogyny in their raps: they are pointing up the negativity to help bring about change. I really don't see young students of mine buying it and saying, "Wow, that's horrible! I think things need to change!" More likely they shout out the rap as an anthem.
In any case, I do not plan on seeing the movie if the subject is as you say. I know any form of media cannot "make" people think a certain way, but if the only way something is presented is in a negative light, then, well, that's most likely how folks will see it. And if you expect to make the point within the context of the movie that this boy is naughty,, ..bad bad for doing this... there is still the contingent who will not see the movie, but think themselves experts knowing about the movie. As was mentioned, the DC sniper already helped further a bad name for the tarot. I can't help seeing that a movie about a boy who grafts the tarot to his skin and uses it as an instrument of evil, supernatural power doing anything but enforcing puritanical witch hunts.
Peace!