Thank you all for your replies. Today was a liiiiiiittle bit better than the previous car rides we have done with him. Not constant screaming. But he still screams, and it’s a scream that can make ears bleed... But anyway, a little better today. He lied down and stayed quiet for about 5-10 minutes of the 20 minute ride. On the way home.
Hopefully if we keep up with daily car rides where he always gets his toys and treats with him, and as long as we go someplace fun every time this will help getting him calmer in the car.
I will also try the Rescue Remedy, it can’t hurt I guess 🙂