Table and Graph next to each other

Expanding on the comments of @leandriis, the following uses minipages, multicolumn, siunitx and subcaption to obtain what you seem to be looking for:

documentclass{article}
usepackage[left=1in,right=1in,top=1in,bottom=1in]{geometry} % page margins
usepackage{graphicx} % multicolumn and includegraphics
usepackage{booktabs} % toprule
usepackage{subcaption} % subcaption
usepackage{siunitx} % S column type (align by decimal)
sisetup{parse-numbers=false} % allow parentheses in number column

begin{document}
setlength{tabcolsep}{0.2em} % reduce separation between table columns

begin{figure}
caption{Linear Regression of Wellbeing on EF.} label{calculatingEWEB}
begin{minipage}{0.55textwidth}
        begin{tabular}{p{4cm} S
 S} % p{4cm} makes the table narrower; S treats entries as numbers (i.e. math mode) and centres on decimal point
        toprule
        Ecological Footprint & 0.139^{mathit{***}} & 0.123^{mathit{***}} 
        & (0.035) & (0.035) 
        Income (linear) && -0.072 
        &&(0.122) 
        Income (quadratic) && 0.016 
        &&(0.013) 
        Income (cubic) &&-0.000 
        && (0.000) 
        Constant & 5.561^{mathit{***}} &5.364^{mathit{***}} 
        & (0.265) & (0.337) 
        midrule
        R-squared & 0.041 & 0.084  
        midrule
        multicolumn{3}{l}{*** p$ < $0.01, ** p$ < $0.05, * p$ < $0.1} 
        % ensures the p-value row can straddle multiple columns 
        end{tabular}
end{minipage}
hfill
begin{minipage}{0.45textwidth}
    subcaption*{Distribution of EWEB.}
    label{fig:EWEBdis}
    includegraphics[width=textwidth]{"<histogram>"}
end{minipage}
end{figure}

end{document}

Here are three different options under the assumption that figure and table should each get their own caption:

documentclass{article}
usepackage{booktabs}
usepackage{siunitx}

usepackage{tabularx}
usepackage{caption}
usepackage[demo]{graphicx}
usepackage[export]{adjustbox}

usepackage{geometry}
begin{document}

begin{table}[ht]
begin{minipage}[t]{0.5textwidth}
caption{Linear Regression of Wellbeing on EF.}
label{calculatingEWEB}
begin{tabular}{lrr}
    toprule
    Ecological Footprint & 0.139*** & 0.123*** 
          & (0.035) & (0.035) 
    Income (linear) && -0.072 
          &&(0.122) 
    Income (quadratic) && 0.016 
          &&(0.013) 
    Income (cubic) &&-0.000 
          && (0.000) 
    Constant & 5.561*** &5.364*** 
          & (0.265) & (0.337) 
    midrule
    R-squared & 0.041 & 0.084  
    midrule
    multicolumn{3}{l}{*** p<0.01, ** p<0.05, * p<0.1}
    end{tabular}
end{minipage}
hfill
begin{minipage}[t]{0.45textwidth}
captionof{figure}{Distribution of EWEB.}
label{fig:EWEBdis}
includegraphics[width=linewidth,valign=c]{Figures/EWEB distrubtion.pdf}
end{minipage}
end{table}

begin{table}[ht]
begin{minipage}[t]{0.5textwidth}
caption{Linear Regression of Wellbeing on EF.}
label{calculatingEWEB}
sisetup{
    input-open-uncertainty   = ,
    input-close-uncertainty  = ,
    table-space-text-post = ***,
    table-space-text-pre = ),
    table-align-text-post=false, 
    table-align-text-pre=false
%    
}
begin{tabular}{l*{2}{S[table-format=1.4]}}
    toprule
    Ecological Footprint & 0.139*** & 0.123*** 
          & (0.035) & (0.035) 
    Income (linear) && -0.072 
          &&(0.122) 
    Income (quadratic) && 0.016 
          &&(0.013) 
    Income (cubic) &&-0.000 
          && (0.000) 
    Constant & 5.561*** &5.364*** 
          & (0.265) & (0.337) 
    midrule
    R-squared & 0.041 & 0.084  
    midrule
    multicolumn{3}{l}{*** p<0.01, ** p<0.05, * p<0.1}
    end{tabular}
end{minipage}
hfill
begin{minipage}[t]{0.45textwidth}
captionof{figure}{Distribution of EWEB.}
label{fig:EWEBdis}
includegraphics[width=linewidth,valign=c]{Figures/EWEB distrubtion.pdf}
end{minipage}
end{table}

begin{table}[ht]
begin{minipage}[t]{0.5textwidth}
centering
caption{Linear Regression of Wellbeing on EF.}
label{calculatingEWEB}
sisetup{
    input-open-uncertainty   = ,
    input-close-uncertainty  = ,
    table-space-text-post = ***,
    table-space-text-pre = ),
    table-align-text-post=false, 
    table-align-text-pre=false
%    
}
begin{tabular}{l*{2}{S[table-format=1.4]}}
    toprule
    Ecological  & 0.139*** & 0.123*** 
      Footprint     & (0.035) & (0.035) 
    addlinespace
    Income  && -0.072 
      (linear)    &&(0.122) 
    addlinespace
    Income  && 0.016 
      (quadratic)      &&(0.013) 
    addlinespace
    Income  &&-0.000 
      (cubic)     && (0.000) 
    addlinespace
    Constant & 5.561*** &5.364*** 
          & (0.265) & (0.337) 
    midrule
    R-squared & 0.041 & 0.084  
    midrule
    multicolumn{3}{l}{*** p<0.01, ** p<0.05, * p<0.1}
    end{tabular}
end{minipage}
hfill
begin{minipage}[t]{0.45textwidth}
captionof{figure}{Distribution of EWEB.}
label{fig:EWEBdis}
includegraphics[width=linewidth,valign=c]{Figures/EWEB distrubtion.pdf}
end{minipage}
end{table}

end{document}