[Tex/LaTex] Subfigure package caption positioning

Question

I would like to use subfigure package, since it allows to define the subfigure environment size in terms of columnwidth, etc.
However, I need to follow some formatting as:

• Figure title on top and align to left (Figure 1 – …);
• Subcaptions below subfigures and
• Figure description on bottom and align to left.

How is it possible?
Thanks in advance

Updated: I've got almost what I need. Only references to subfigure are not right yet.

\documentclass{article}
\usepackage{mwe}

\newcounter{subfig}[figure]
\renewcommand{\thesubfig}{\alph{subfig}}

\newcommand{\subcaption}[1]% #1 = caption text
{\par\stepcounter{subfig}%
\makebox[\textwidth]{\textbf{(\thesubfig)} #1}%
\medskip\par}

\newenvironment{subfigure}[1]% width
{\begin{minipage}{#1}\let\caption=\subcaption}%
{\end{minipage}}
\usepackage[justification=justified,singlelinecheck=false,labelsep=endash,position=top]{caption}

\begin{document}
\begin{figure}[t]
\caption{Test 1}
\begin{subfigure}{0.45\columnwidth}
\centering\includegraphics[width=\textwidth]{example-image-a}%
\label{fig:test11}
\caption{}
\end{subfigure}\hfill
\begin{subfigure}{0.45\columnwidth}
\centering\includegraphics[width=\textwidth]{example-image-b}%
\label{fig:test12}
\caption{}
\end{subfigure}
\label{fig:test1}\\
{\footnotesize Source: Here comes the figures description.}
\end{figure}

\begin{figure}[!h]
\caption{Test 2}
\begin{center}
\centering\includegraphics[width=0.6\columnwidth]{example-image-c}
\end{center}
\label{fig:test2}
{\footnotesize Source: Here comes the figures description.}
\end{figure}

Figures \ref{fig:test1} is composed of \ref{fig:test11} e \ref{fig:test12}.

Figure \ref{fig:test2} is an ordinary include entry.
\end{document}

Here the output:

Answer 1

See, if this modification of your MWE do what you like to have:

\documentclass{article}
\usepackage{mwe}
\usepackage[justification=justified,
            singlelinecheck=false,
            labelsep=endash,
            position=top]{caption}
\usepackage[justification=centering]{subcaption}

\begin{document}
    \begin{figure}[t]
\caption{Test 1}
\label{fig:test1}
    \begin{subfigure}{0.45\columnwidth}
    \centering
\includegraphics[width=\linewidth]{example-image-a}%
\caption{}
    \label{fig:test11}
    \end{subfigure}
\hfill
    \begin{subfigure}{0.45\columnwidth}
    \centering
\includegraphics[width=\linewidth]{example-image-b}%
    \caption{}
\label{fig:test12}
    \end{subfigure}

{\footnotesize Source: Here comes the figures description.}
\end{figure}

\begin{figure}[!h]
    \centering
\caption{Test 2}
\label{fig:test2}
\includegraphics[width=0.6\columnwidth]{example-image-c}

\begin{minipage}{\linewidth}\footnotesize 
Source: Here comes the figures description.
\end{minipage}
\end{figure}

Figures \ref{fig:test1} is composed of \ref{fig:test11} e \ref{fig:test12}. 
Figure \ref{fig:test2} is an ordinary include entry.
\end{document}

In above MWE I remove your definitions of subfigure counter and environment and instead them use package subcaption. Beside this I put labels after captions where they should be (for correct referencing)