Looking for a source for the kapitlach tehillim too.
These 7 kapitelach in the same order are what’s listed in one of the Halacha Seforim on death and mourning, to be said at the gravesite on a yahrtzeit. Also listed is to recite the letters of the deceased‘s name and the letters נשמה from chapter קיט
Not sure what the significance of these 7 is though.