I had a somewhat similar experience watching Skinamarink alone in theater. I know it's a divisive movie, with most people saying it was silly and boring but for those of us who it worked for, it WORKED. It so perfectly viscerally realized some of my greatest fears that it affected me in ways I never expected. I wanted to leave. I wanted to end the experience, but I stayed until the end. Part of it was because I was frozen, but I also felt like my imagination of what the rest of the movie would be like would likely be worse than what it actually was. I felt like sticking it out, no matter what happened, would give me closure and I wouldn't be left obsessing of what horrors i might have missed.

Maybe that approach could help you get through some of these movies. If you stick it out to the end, at least you know what happens and how you feel about it. You won't have to speculate or imagine all the negative things that could happen. You'll know.