When my son was younger and became nervous or over stimulated I found doing "feather touches" up and down his arm would calm him to almost a comatose state, which might sound extreme but it was his escape. He's now 17 and the "feather touch" still saves him from stresses. Finding a way to redirect him will save you many tantrums.
I wish you the best in the journey.

How much sugar had he had that day and food coloring in any of his food?
I discovered sugar and red and green food dye set Lizzie off. Also we did bathtime to help chill her out a lot.

i have no idea why he would be screaming , if it was only at night i would say maybe it was growing pains . on the other head the cars cartoons i think its harmless my son would do the same thing , cartoons over and over aover agian ... i got him portable dvd player ..to go everywhere with us . and to be honest cartoons help my son tons ... he reinacts everything and sings along ! and used some of the words off the cartoon in real life events ...

I know its probably not the answear you want to here but the best advice given to me was that it is ok to let an autistic child have there down time (cars movie). I didn't like my child zoning out on tv or other electronics because the transistion from that would start a whole new tantrum..But, Just imagine living in a world were every sound is like a freight train in your head and every light is like a flash light being shone in your eyes, every touch a creepy crawly touch. If I felt like that and couldn't escape it I would cry for hours too and want to have moments of peice.. I believe the reason they enjoy it so much is because they can be at peice with themselves for those moments in time. Continue working on the therapy's and as time goes on and your child can learn to control himselve you can slowly work twards having less zoning out time.
Hope this helps :)

A lot of our kids have obsessive interests. It is normal for then to hyper focus be it on a movie or a specific thing like dinosaurs. I do not think that removing the thing your child is obsessed with will remove his need to fixate on something. For example, in this situation, taking away the Cars movies might eventually eliminate his obsession with it but he will more than likely just move on to a new obsession.

You might want to try working with the obsession instead of against it. Go get that movie on DVD (if you don't already own it) and use it as a tool to help you. Any high interest item can be incredibly motivational for a child to improve behavior, communication, and learning. If he uses appropriate language when asking, let him watch the movie for a bit. Go get a Cars coloring book or print out pictures of Lightning McQueen from the internet that he can color or hang on his bedroom walls. I'm sure you get the idea. Good luck :)