Pull-up bar help!

I've been doing the You Are Your Own Gym Basic program, and tomorrow (bright and early) I have to do (assisted) pull-ups. The app says to do them on my door, but I was worried about breaking the door, so I bought a doorway pull-up bar...and it doesn't fit my door. Am I doing something wrong? Is there a trick? It seems like the door frame is about a half-inch too thick, but maybe I am just doing some stupid thing wrong?

AND if the bar I have really just won't work, I'm thinking I should go ahead and use the door, but will I break it? The app says to put a towel across the top of the door (for my hands, I guess) and a second towel over the hinge (to stop it swinging). Then I'd be doing "pull-ups" with some of my weight on my feet, which will be on a chair. I live in an old house with big, solid doors, but I'm sure the hinges weren't designed for someone to hang from the door. I weigh 154 pounds, so possibly (?) less than the YAYOG video demo guy, but I'm not a lightweight. Has anyone done this? Does anyone know if the door can take my weight? I can't do a pull-up, so decent amount of my weight will have to be on my feet, but I did intend to really try to make it as real as possible.