Now here's the thing... after about a year of following the PBF program, i've reached above level 4 on every bw exercise in the program, except for pull ups/chin ups (maxed out push ups, squats and planks, still stuck on half handstand pushups), and after reading the simplefit requirements, i think it's because maybe i've been doing the wrong: you see, i don't use a pull up bar...
I use this:

As you can see, i use an old towel for better grip (there's this small gap that makes it painful to hold normally), it has a standard doorway height and the "bar" part is too wide to close my hand around it. I keep my arms close to my head (between the two small bars at each side), and am able to actully raise my chin above the "bar" and mostly pull 8 to 10 consecutive ones before failure; PBF calls for 12 consecutive ones before mastering basic pull/chin ups, -when i try to pull those last 4, or 2, i mostly reach forehead level and barely can control my drop.
What do you think? Am i doing it wrong? Any tips or suggestions? Right now, getting a pull up bar is out of my budget and ALL my doors are like those in the pic, so no frame.
I really hope you guys can help me with this. Thanks in advance and keep strong!