Every fpkg theme is non-permanent. When you turn your console off, you have to run the exploit and select the theme again. This theme isn't from PSN, Crazy Potato made it. You were rude for no reason.
I assume that you have the PC version of MKXL, correct?
Did you actually get 'cheat engine' to work in the PS4? I never tried it, assuming that it wouldn't work.
This is a similar method for getting Dead or Alive characters/costumes. There is a thread here on the PC version...
Which texture mods and npc replacers, specifically? Although, off the top of my head, it sound to me like you're having problems with large uncompressed textures.