How to make a landscape table fill the whole width?

It seems that neither textwidth nor textheight can force the table to fill the whole width.

documentclass[dvips]{book}
usepackage[a4paper,margin=20mm,showframe]{geometry}
usepackage{lscape}
usepackage{lipsum}
usepackage{calc}
usepackage{longtable,array}

begin{document}
chapter{One}
lipsum[1]
section{One One}
lipsum[2]

pagestyle{empty}
begin{landscape}
begin{longtable}{|m{0.4textheight-2tabcolsep-1.5fboxrule}|m{0.6textheight-2tabcolsep-1.5fboxrule}|}
hline
a & b\hline
c & d\hline
end{longtable}
end{landscape}
pagestyle{plain}

lipsum[3]
end{document}

EDIT 1:

I made a correction in the column width, i.e., changing 2fboxrule to 1.5fboxrule. The former calculation is wrong because the rule between 2 columns should NOT be calculated twice. I slipped a little here.

And I got an output as follows:

EDIT 2: It’s my real scenario (as opposed to the minimal code)

documentclass[dvipsnames,rgb,dvips]{book}

usepackage[a4paper,margin=20mm,showframe]{geometry}
usepackage{longtable}
usepackage{array}
usepackage{calc}
usepackage{ltablex}
usepackage{lscape}

newcounter{No}
renewcommand{theNo}{stepcounter{No}arabic{No}}
newenvironment{MyTable}[4]%
{%
    newcolumntype{A}[1]%
    {%
        >{%
            begin{minipage}%
                {%
                    ##1textwidth-2tabcolsep-1.5arrayrulewidth%
                }%
                vspace{tabcolsep}%
         }%
         c%
        <{vspace{tabcolsep}end{minipage}}%
    }%
    setcounter{No}{0}%comment out this if you want to continuous numbering for all tables.
    begin{longtable}%
    {%
            |>{scriptsizecenteringtheNo}A{#1}<{}%
            |>{}A{#2}<{centeringinput{jobname.tmp}}%
            |>{centeringlstinputlisting{jobname.tmp}}A{#3}<{}%
            |>{scriptsizearraybackslash}A{#4}<{}%
            |%
    }%
    hlineignorespaces%
}%
{%
    end{longtable}%
}

newcommand{Comment}[1]{& & & #1\hline}


usepackage{listings}
lstset{%
language={PSTricks},
basicstyle=ttfamilyscriptsize,%
keywordstyle=color{blue}%,
%backgroundcolor=color{yellow!30}%
}
usepackage{fancyvrb}


defMyRow{%        
        VerbatimEnvironment%
        begin{VerbatimOut}{jobname.tmp}%
}

defendMyRow{%
        end{VerbatimOut}%      
}



usepackage{pstricks,pst-node}
newpsstyle{gridstyle}{%
gridwidth=0.4pt,%default: 0.8pt
gridcolor=Red!20,%default: black
griddots=0,%default: 0 
%
gridlabels=3pt,%default: 10pt
gridlabelcolor=Blue,%default: black
%
subgriddiv=5,%default: 5
subgridwidth=0.2pt,%default: 0.4pt
subgridcolor=Green!20,%default: gray
subgriddots=0%default: 0
}

usepackage{lipsum}

begin{document}
chapter{Introduction to PSTricks}
lipsum[1]

section{At a glance galleries}
lipsum[1-5]

%Landscape starts here.
%pagestyle{empty}
begin{landscape}
thispagestyle{empty}
begin{MyTable}{0.05}{.25}{0.4}{0.3}%
%=============
begin{MyRow}
pspicture*[showgrid](4,4)
pnode(1,1){A}
pnode(3,3){B}
ncline{A}{B}
endpspicture
end{MyRow}
Comment{lipsum[1]}
%=============
begin{MyRow}
begin{pspicture}[showgrid](4,3)
psframe*[linecolor=red!30](3,2)
end{pspicture}
end{MyRow}
Comment{lipsum[2]}
%=============
begin{MyRow}
pspicture[showgrid](4,3)
psframe*[linecolor=green!30](3,2)
endpspicture
end{MyRow}
Comment{lipsum[3]}
%=============
begin{MyRow}
pspicture[showgrid](4,3)
psframe*[linecolor=yellow!30](3,2)
endpspicture
end{MyRow}
Comment{lipsum[4]}
%=============
begin{MyRow}
pspicture[showgrid](4,3)
psframe*[linecolor=Maroon!30](3,2)
endpspicture
end{MyRow}
Comment{lipsum[5]}
%=============
end{MyTable}
%Landscape stops here.
end{landscape}
%pagestyle{plain}

section{Node}
lipsum[1-5]
end{document}

Unfortunately, arrayrulewidth does not work.

EDIT 3:

dvips has been added for both code snippets above. The arrayrulewidth still cannot work the way we want.