ClassicThesis Typography Masterpiece

\documentclass[11pt,paper=a4,footinclude=true,headinclude=true,open=any]{scrbook}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[parts=false,eulerchapternumbers]{classicthesis}

% ---------------------------------------------------------------------
% Palette: four custom colours, then re-skin classicthesis' own
% internal named colours so links, citations and chapter numerals
% follow the same palette instead of the package defaults.
% ---------------------------------------------------------------------
\definecolor{claybrick}{RGB}{150,58,42}
\definecolor{slatestone}{RGB}{54,70,82}
\definecolor{parchment}{RGB}{247,242,232}
\definecolor{umberink}{RGB}{40,34,29}

\definecolor{CTtitle}{RGB}{150,58,42}
\definecolor{CTlink}{RGB}{54,70,82}
\definecolor{CTurl}{RGB}{54,70,82}
\definecolor{CTcitation}{RGB}{54,70,82}
\definecolor{CTsemi}{RGB}{178,170,160}

\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{epigraph}
\usepackage{tikz}
\usepackage{tcolorbox}

\setlength{\epigraphwidth}{0.62\textwidth}
\renewcommand{\epigraphflush}{flushright}
\setlength{\epigraphrule}{0pt}

\tcbset{
  colframe=slatestone,
  colback=parchment,
  colbacktitle=slatestone,
  coltitle=parchment,
  fonttitle=\spacedlowsmallcaps,
  boxrule=0.5pt,
  arc=0pt,
  left=8pt,right=8pt,top=5pt,bottom=5pt