Header only on first page, smaller margins on subsequent pages with multicol and landscape

My current code is below. I want the header in this landscape document only on the first page, and not on any subsequent pages. Furthermore, I want to remove the big gap that happens when I suppress the header on subsequent pages. Thus, what I currently do, is end multicol after the first page, then define a newgeometry that applies to subsequent pages. This has the disadvantage, that I have to manually fill the first page, then apply the end multicol and newgeometry. Overall this seems like a hacky solution.

Does anyone have an idea how to make this code more elegant?

documentclass[11pt,a4paper]{article}
usepackage[english]{babel}
usepackage{fancyhdr}
usepackage{multicol}
usepackage[usegeometry]{typearea}% before geometry!
usepackage{geometry}
usepackage{hanging}
usepackage{amsmath}
usepackage{amssymb}

newcommand*{uselandscape}{%
  clearpage
  KOMAoptions{paper=landscape,DIV=current}%switch to landscape
  newgeometry{% geometry settings for landscape
    left=0.3in, right=0.3in, top=0.9in, bottom=0.8in,headheight=23pt
  }%
}

pagestyle{plain}
cfoot{thepage}

fancypagestyle{firstpage}
{
    fancyhead[L]{HeaderHeader 2 (last updated today)}
}


begin{document}

thispagestyle{firstpage}
uselandscape

begin{multicols*}{3}

section{Preferences and Choice}
hangpara{1em}{1}textbf{Rational preference relation} the preference relation $succsim$ is rational iff it satisfies 
begin{enumerate}
    item Completeness: $forall x,y, xsuccsim y$ or $y succsim x$
    item Transitivity: $forall x,y,z, xsuccsim y$ and $y succsim z implies xsuccsim z$ 
    end{enumerate}
If $succsim$ is rational, then 
begin{enumerate}
    item $succ$ is both irreflexive ($xsucc x$ never holds) and transitive (if $xsucc y$ and $ysucc z$ then $xsucc z$)
    item $forall x,y,z, xsuccsim y$ and $y succsim z implies xsuccsim z$ 
    item if $xsucc y succsim z,$ then $xsucc z$
    end{enumerate}
    

end{multicols*} % end multicols after first page to define newgeometry for all subsequent pages

newgeometry{% newgeometry settings for subsequent pages: top margin 0.1in and no header
    left=0.3in, right=0.3in, top=0.1in, bottom=0.7in,headheight=0pt,includehead
  }%
begin{multicols*}{3}

hangpara{1em}{1}textbf{An Unnumbered Paragraph} aaa
end{multicols*}

end{document} 

documentclass[11pt,a4paper]{article}
usepackage[english]{babel}
usepackage{fancyhdr}
usepackage{multicol}
usepackage[usegeometry]{typearea}% before geometry!
usepackage{geometry}
usepackage{hanging}
usepackage{amsmath}
usepackage{amssymb}

newcommand*{uselandscape}{%
  clearpage
  KOMAoptions{paper=landscape,DIV=current}%switch to landscape
  newgeometry{% geometry settings for landscape
    left=0.3in, right=0.3in, top=0.9in, bottom=0.8in,headheight=23pt
  }%
}

pagestyle{plain}
cfoot{thepage}

fancypagestyle{firstpage}
{
    fancyhead[L]{HeaderHeader 2 (last updated today)}
}


begin{document}

thispagestyle{firstpage}
uselandscape

begin{multicols*}{3}

section{Preferences and Choice}
hangpara{1em}{1}textbf{Rational preference relation} the preference relation $succsim$ is rational iff it satisfies 
begin{enumerate}
    item Completeness: $forall x,y, xsuccsim y$ or $y succsim x$
    item Transitivity: $forall x,y,z, xsuccsim y$ and $y succsim z implies xsuccsim z$ 
    end{enumerate}
If $succsim$ is rational, then 
begin{enumerate}
    item $succ$ is both irreflexive ($xsucc x$ never holds) and transitive (if $xsucc y$ and $ysucc z$ then $xsucc z$)
    item $forall x,y,z, xsuccsim y$ and $y succsim z implies xsuccsim z$ 
    item if $xsucc y succsim z,$ then $xsucc z$
    end{enumerate}
    

%end{multicols*} % end multicols after first page to define newgeometry for all subsequent pages

newpage
newgeometry{% newgeometry settings for subsequent pages: top margin 0.0in and no header
    left=0.3in, right=0.3in, top=0.0in, bottom=0.7in,headheight=0pt,includehead
  }%
%begin{multicols*}{3}

hangpara{1em}{1}textbf{An Unnumbered Paragraph} aaa

newpage

hangpara{1em}{1}textbf{Another Unnumbered Paragraph} bbb


end{multicols*}
end{document}