Btukfyl

I am formatting a book using LuaLaTex.
I need to obtain headers like

and

and I am using the titlesec package.
I need therefore that the page numbers are outside the standard textwidth.
So far the best I could do is

documentclass[10pt]{book}



usepackage{fontspec}

%setmainfont[Ligatures=TeX]{Apollo MT}



usepackage[svgnames]{xcolor}

usepackage{titlesec}

usepackage{lipsum}

usepackage[many]{tcolorbox}% environment for colored and framed text boxes with a heading line



usepackage[vcentering, hcentering, inner=10.5mm,outer=10.5mm,top=25.5mm, bottom=25.5mm,showframe]{geometry} % Extended page layout customization

geometry{papersize={189mm,246mm}} % Possible dimensions of textbook pages



 %Page headers

%colored box for page numbers

newtcbox{mypagenum}{enhanced,nobeforeafter,tcbox raise base,boxrule=1pt,top=0mm,bottom=0mm,

  colframe=red,coltext=black,colback=white, halign = right,

    width=2.55cm,arc=3.5mm, sharp corners=west, boxsep=2mm,

  } 





newpagestyle{main}{

   sethead[thesection~sectiontitle~mypagenumthepage]  % even

           {mypagenumthepage Chapter thechapterchaptertitle}{}{} % odd

           }

pagestyle{main}



begin{document}



chapter{My title}

lipsum[20-30]

section{My Section}

lipsum[20-30]

end{document}

and I cannot find a (simple) way to extend the header width or position the page number with something like hspace{-XXcm}.