Hanging Indentation of Chapter Header text

Question

Currently, the Section header text indentation is hanged thanks to @Simon Dispa solution at Misalignment caused by hyphenat package and header text font settings. I also want to have my Chapter header text indentation be hanged just like that of the Section. Below is the MWE:

\documentclass[12pt,openany,twoside]{book}
\raggedbottom
\usepackage[ 
left=2.5cm,
right=2.5cm, 
top=3cm, 
bottom=3cm,
headheight = 3\baselineskip,
headsep = 5mm,
a4paper
]{geometry}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage[table]{xcolor}
\usepackage{graphicx}
\newcommand\HRule{\noindent\rule{\linewidth}{1.5pt}}
\usepackage{background}
\backgroundsetup{contents={}}
\usepackage{fancyhdr}
\usepackage{hhline}


\newcommand*\myheaderfooterfont{\normalfont\bfseries\selectfont}
\newlength{\leftspace}% 
\setlength{\leftspace}{18ex}%
\newlength{\xindent}
\settowidth{\xindent}{\myheaderfooterfont\thechapter.\thesection\:}
\usepackage{varwidth}% 


\fancypagestyle{fancy}{%
    \fancyhf{}
    \fancyhead[OL]{\leftmark}
    \fancyhead[ER]{\begin{varwidth}{\dimexpr\textwidth-\leftspace}\myheaderfooterfont\raggedright\parindent-\xindent\rightmark\end{varwidth}}
    \fancyfoot{}
    \fancyfoot[RE,RO]{\thepage}
    \renewcommand\headrule
    {{     \color{blue}\rule{1\headwidth}{2.5pt}%       
    }}
}

\fancypagestyle{plain}{%
    \fancyhf{}%
    \renewcommand\headrule
    {{     \color{blue}\rule{1\headwidth}{0pt}%         
    }}      
}

\pagestyle{fancy}   

\usepackage{showframe}

\usepackage[none]{hyphenat}
\raggedright

\begin{document} 
    %<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<added
    \frontmatter
    \chapter*{ABC}
    \markboth{ABC}{ABC}
    eeeheeyeyeyeyeyeeyeye
    \section*{DEG}
    dddheheheheheheheehehehe
    \pagebreak
    \section*{KJ}
    ddhheheheheheehehehheheheheheh
    \pagebreak
    \section*{KDH}
    dhddhhehehehehehehehehehehe

    \mainmatter
    %<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<added
    \chapter{ABCD ffhfgrhr ejejejeje fhfhfhf ehehehehe dhddhdhellgl rkttkgkhihi eeeejejwnwn hhlhlnnmgjgj rjrrjoaoaoao rjjrjrrrj wwjwwwjwjw}
    
    eehehdhdhdhdddddd ddddddddddddddddddddd
    
    \pagebreak
    
    \section{Special keyboard characters gghthr rhrrhd fheheh fhehuw fhewiwi feiwiwd fiiwiwid fiiwiwi firiifn rokfkkvfvv fjjjeje jejeje djej}   
    
    
    \LaTeX{} has many symbols at its disposal. The majority of them are within the mathematical domain as shown in \eqref{eq:1} and \eqref{eq:2}. The ten special keyboard characters are: \verb|#|, \verb|$|, \verb|%|, \verb|&|, \verb|~|, \verb|_|, \verb|^|, \verb|\| and  \verb|{}|. If you simply want the character to be printed just as any other letter, include a \verb|\ | in front of the character. For example, \verb|\$| will produce \verb|$| in your output.
    The exception to the rule is the \verb|\ | itself because \verb|\\ | has its own special meaning. A \verb|\ | is produced by typing \verb|$\backslash$| in your file. 
    
    \clearpage
    
    Special keyboard characters dhgdgdg dgdgdgdg ggdgdgd egegegege dgddgdgd eggegegeg dgdgdgdgd egegegeg dggeieieirr tktii43iwje rfrhrhrhr gtktotyiyighgjgj fkf      
Some text.
\end{document}

Answer 1

UPDATE Changing the header font.

Try this code.

Last update: matching spaces and taller headheight.

% !TeX TS-program = pdflatex    
\documentclass[12pt,openany,twoside]{book}
\raggedbottom
\usepackage[ 
left=2.5cm,
right=2.5cm, 
top=3cm, 
bottom=3cm,
headheight = 3.5\baselineskip,%<<<<<<<<<<<<<<<<<<
headsep = 5mm,
a4paper
]{geometry}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage[table]{xcolor}
\usepackage{graphicx}
\newcommand\HRule{\noindent\rule{\linewidth}{1.5pt}}
\usepackage{background}
\backgroundsetup{contents={}}
\usepackage{fancyhdr}
\usepackage{hhline} 

\usepackage{helvet}%<<<<<<<<<<<<<<<<<<<<

%****************************************
\usepackage{tabularx}% added <<<<<      
\newcommand*\myheaderfooterfont{\sffamily\bfseries\selectfont}  

\newlength{\leftspace}% for sections <<<<<<<<<
\setlength{\leftspace}{20ex}%set

\newlength{\Lheader}
\renewcommand{\chaptermark}[1]{\markboth{\uppercase{#1}}{}}% added <<<<<<<<<<<
\renewcommand{\sectionmark}[1]{\markright{\uppercase{#1}}}% added <<<<<<<<<<<

\fancypagestyle{fancy}{%
    \fancyhf{}  
    \fancyhead[OL]{\myheaderfooterfont%
        \ifnum\value{chapter}>0%
        \begin{tabularx}{\textwidth}{@{}lX}\uppercase{Chapter~\thechapter}&\raggedright\leftmark\end{tabularx}% changed <<<<<<<<<<
            \else\raggedright\leftmark\relax\fi}
        \fancyhead[ER]{\myheaderfooterfont%
                \settowidth{\Lheader}{\thesection\hspace*{12pt}\rightmark}  
                \ifnum\value{chapter}>0%
                \ifdim\Lheader>\linewidth%          
                \begin{tabularx}{\dimexpr\textwidth-\leftspace}{@{}lX} \thesection &\raggedright\rightmark\end{tabularx}%
                \else\begin{tabular}{@{}ll@{}} \thesection &\raggedright\rightmark\end{tabular}%
                \fi\else\hfill\raggedright\rightmark\relax\fi
    }% changed <<<<<
                
    \fancyfoot[RE,RO]{\thepage}
    \renewcommand\headrule{\color{blue}\rule{1\headwidth}{2.5pt}}
}
%****************************************

\fancypagestyle{plain}{%
    \fancyhf{}%
    \renewcommand\headrule
    {{     \color{blue}\rule{1\headwidth}{0pt}%         
    }}      
}

\pagestyle{fancy}   

\usepackage{showframe}

\usepackage[none]{hyphenat}
\raggedright %  important with  none hyphenat + none !!!!!!!!!!!!!!!!!

\begin{document} 
    
    \frontmatter
    \chapter*{ABC}
    
    \markboth{ABC1}{ABC2}
    
    eeeheeyeyeyeyeyeeyeye
    \section*{DEG}
    dddheheheheheheheehehehe
    \pagebreak
    \section*{KJ}
    ddhheheheheheehehehheheheheheh
    \pagebreak
    \section*{KDH}
    dhddhhehehehehehehehehehehe
    
    \mainmatter

    \chapter{ABCD ffhfgrhr ejejejeje fhfhfhf ehehehehe dhddhdhellgl rkttkgkhihi eeeejejwnwn hhlhlnnmgjgj rjrrjoaoaoao  }        
    eehehdhdhdhdddddd ddddddddddddddddddddd     
        
    \newpage                
    \section{Special keyboard characters gghthr rhrrhd fheheh fhehuw fhewiwi feiwiwd fiiwiwid fiiwiwi}  

    \LaTeX{} hasmany symbols at its disposal. The majority of them are within the mathematical domain as shown in \eqref{eq:1} and \eqref{eq:2}. The ten special keyboard characters are: \verb|#|, \verb|$|, \verb|%|, \verb|&|, \verb|~|, \verb|_|, \verb|^|, \verb|\| and  \verb|{}|. If you simply want the character to be printed just as any other letter, include a \verb|\ | in front of the character. For example, \verb|\$| will produce \verb|$| in your output.
    The exception to the rule is the \verb|\ | itself because \verb|\\ | has its own special meaning. A \verb|\ | is produced by typing \verb|$\backslash$| in your file.       
    \newpage        
    \section{Special keyboard characters}       
    Special keyboard characters dhgdgdg dgdgdgdg ggdgdgd egegegege dgddgdgd eggegegeg dgdgdgdgd egegegeg dggeieieirr tktii43iwje rfrhrhrhr gtktotyiyighgjgj fkf     
    \newpage        
    Special keyboard characters dhgdgdg dgdgdgdg ggdgdgd egegegege dgddgdgd eggegegeg dgdgdgdgd egegegeg dggeieieirr tktii43iwje rfrhrhrhr gtktotyiyighgjgj fkf
                   
    \chapter{One short line}        
    \LaTeX{} has many symbols at its disposal. The majority of them are within the mathematical domain as shown in \eqref{eq:1} and \eqref{eq:2}. The ten special keyboard characters are: \verb|#|, \verb|$|, \verb|%|, \verb|&|, \verb|~|, \verb|_|, \verb|^|, \verb|\| and  \verb|{}|. If you simply want the character to be printed just as any other letter, include a \verb|\ | in front of the character. For example, \verb|\$| will produce \verb|$| in your output.
    The exception to the rule is the \verb|\ | itself because \verb|\\ | has its own special meaning. A \verb|\ | is produced by typing \verb|$\backslash$| in your file. 
    
    \section{Special keyboard characters}   
    Special keyboard characters dhgdgdg dgdgdgdg ggdgdgd egegegege dgddgdgd eggegegeg dgdgdgdgd egegegeg dggeieieirr tktii43iwje rfrhrhrhr gtktotyiyighgjgj fkf     
    \newpage        
    Special keyboard characters dhgdgdg dgdgdgdg ggdgdgd egegegege dgddgdgd eggegegeg dgdgdgdgd egegegeg dggeieieirr tktii43iwje rfrhrhrhr gtktotyiyighgjgj fkf     
    \newpage        
    Special keyboard characters dhgdgdg dgdgdgdg ggdgdgd egegegege dgddgdgd eggegegeg dgdgdgdgd egegegeg dggeieieirr tktii43iwje rfrhrhrhr gtktotyiyighgjgj fkf     

\end{document}