KOMA script: Appendix sections A1.1, A1.2, ... A2.1 and uppercase TOC chapter entries

I use xelatex with KOMA script class scrreprt. Now I have to number my thesis appendices as sections A1.1, A1.2 and subsections A1.1.1, and so on. Chapter entries in the TOC including chapter APPENDICES should be set uppercase.

Therefore, I redefined the \thesection and \thesubsection. The hyperref option hypertexnames=false makes sure that the links are linked correctly. But now I want the TOC entries A1.1, ... aligned with the normal sections and subsections numbers like:

 1.1 Section
     1.1.1 Subsection
A1.1 Appendix Section
    A1.1.1 Appendix Subsection

Setting the main font Verdana with fontspec additionally leads to reduced spacing between A1.1 and the corresponding TOC entry:

This might by caused by not defining A as an appedix prefix.

Further, I tried to make the TOC chapter entries uppercase with:

\addtokomafont{chapterentry}{\MakeUppercase} 

But this produces error messages for the .toc file. Somehow this works fine for chapter titles in the text itself and also \nameref chapter is not uppercase as intended.

I hope anyone can help me with the appendix entry alignment and the uppercase chapter entry. Thank you in advance!

Here is my MWE:

% !TEX TS-program = xelatex

\documentclass[
a4paper,
10pt,
]{scrreprt}

\usepackage[no-math]{fontspec}
\PassOptionsToPackage{no-math}{fontspec}

\usepackage{footnotebackref}

\usepackage[showframe]{geometry}

\setmainfont[BoldFont={Verdanab.ttf},ItalicFont={Verdanai.ttf}]{Verdana.ttf} % <<< Reduces spacing in toc entries

\setlength{\parindent}{0pt}

% Chapter title
\setkomafont{chapter}{\Large\normalfont\bfseries\MakeUppercase}
\RedeclareSectionCommand[beforeskip=0pt]{chapter}

% TOC entry chapter level
\RedeclareSectionCommand[
toclinefill=\TOCLineLeaderFill
]{chapter}

\setkomafont{chapterentry}{\normalfont\bfseries}
%\addtokomafont{chapterentry}{\MakeUppercase} % <<< This does not work


% Section title
\setkomafont{section}{\large\normalfont\bfseries}

% Subsection/Subsubsection title
\setkomafont{subsection}{\normalsize\normalfont\bfseries}

\hypersetup{ 
    hypertexnames=false,
    colorlinks=true,
    citecolor=black,
    linkcolor=black,
    urlcolor=black,
    bookmarksnumbered,
    bookmarksdepth=2,
    bookmarksopenlevel=1,
    bookmarksopen=true,
} 

\begin{document}

\tableofcontents

\chapter{Main Body}

Reference to appedix \ref{app: First Appendix} or sub-appendix \ref{app: First Sub-Appendix}

\section{Section}

\subsection{Subsetion}

\chapter{Appendices}

\renewcommand{\thesection}{A\arabic{chapter}.\arabic{section}}
\renewcommand{\thesubsection}{A\arabic{chapter}.\arabic{section}.\arabic{subsection}}
\renewcommand{\thesubsubsection}{A\arabic{chapter}.\arabic{section}.\arabic{subsection}.\arabic{subsubsection}}
\setcounter{chapter}{1}
\setcounter{section}{0}
\setcounter{subsection}{0}
\setcounter{subsubsection}{0}

\section{First Appendix} \label{app: First Appendix}

\subsection{Fist Sub-Appendix} \label{app: First Sub-Appendix}

\end{document}