I thought "Suttree" was your favorite McCarthy
That one was actually my previous answer to the "desert island book" question when asked by a friend of mine who actually shared the same answer (he's a huge McCarthy fan and was the main person who told me to read it). Still probably my favorite book of prose and a damn good answer to that question given how long it is and how impressive McCarthy's imagery is throughout the novel. Definitely need to reread it at some point.
Doesn't rumination disorder have to do with spitting up undigested food? Or are you reappropriating the term as a description of your inability to let go of childhood trauma? Maybe "obsessive thinking" is a better term?