LaTeX tabular column formatting

% Source: https://tex.stackexchange.com/questions/598089/columns-horizontal-alignment/598091#598091
\documentclass[a4paper,landscape]{article}

\usepackage{graphicx}
\usepackage{multirow}
\usepackage{amsmath,amssymb}
\usepackage[margin=2.5cm]{geometry}
\usepackage{array}

\newcolumntype{P}{>{\centering\arraybackslash}p{6em}}

\begin{document}
    \begin{table}[!h]
        \caption{Análise de Sensibilidade dos parâmetros $\overline{N u}_{L_{p}}$ e $R a_{L_{P}}$, em função das respectivas incertezas de medição de influência.}
        %
        \begin{tabular}{c*{4}{|P}|c*{1}{|P}|c}
        \hline
        \multirow{2}{*}{
            \begin{tabular}[c]{@{}c@{}}Variação Percentual da\\ Incerteza de Medição\end{tabular}} &
            \multicolumn{5}{c|}{
                Variação Percentual do $\delta_{\overline{N u}_{L_{p}}}$, conforme variações nas incertezas:
            }
&
\multicolumn{2}{c}{
    \parbox{16em}{
        \centering\smallskip
        Variação Percentual do $\delta_{R a_{L_{p}}}$,
        conforme variações nas incertezas:
        \smallskip
    }
}
\\ \cline{2-8}
                                                                                                               & $\delta _{C_{t}}$ & $\delta _{m_{P}}$ & $\delta _{L_{P}}$ & $\delta _{\epsilon}$ & $\delta _{\overline{T}_{\text {inicial}}} = \delta _{\overline{T}_{\text {final}}} = \delta _{\overline{T}_{\infty}}$ & $\delta _{L_{P}}$ & $\delta _{\overline{T}_{\text {inicial}}} = \delta _{\overline{T}_{\text {final}}} = \delta _{\overline{T}_{\infty}}$ \\ \hline
        -90\%                                                                                                  & -0,1058\%         & -0,0797\%         & -0,0029\%         & -88,0945\%           & -0,0204\%                                                                                                             & -0,0879\%         & -89,1567\%                                                                                                            \\ \hline
        -75\%                                                                                                  & -0,1002\%         & -0,0755\%         & -0,0028\%         & -74,2216\%           & -0,0193\%                                                                                                             & -0,0833\%         & -74,6693\%                                                                                                            \\ \hline
        -50\%                                                                                                  & -0,0801\%         & -0,0604\%         & -0,0022\%         & -49,6848\%           & -0,0154\%                                                                                                             & -0,0666\%         & -49,8670\%                                                                                                            \\ \hline
        -25\%                                                                                                  & -0,0467\%         & -0,0352\%         & -0,0013\%         & -24,8771\%           & -0,0090\%                                                                                                             & -0,0388\%         & -24,9482\%                                                                                                            \\ \hline
        +25\%                                                                                                  & 0,0601\%          & 0,0453\%          & 0,0017\%          & 24,9051\%            & 0,0116\%                                                                                                              & +0,0499\%         & +24,9600\%                                                                                                            \\ \hline
        +50\%                                                                                                  & 0,1334\%          & 0,1006\%          & 0,0037\%          & 49,8242\%            & 0,0257\%                                                                                                              & +0,1109\%         & +49,9260\%                                                                                                            \\ \hline
        +75\%                                                                                                  & 0,2200\%          & 0,1659\%          & 0,0061\%          & 74,7514\%            & 0,0424\%                                                                                                              & +0,1829\%         & +74,8953\%                                                                                                            \\ \hline
        +90\%                                                                                                  & 0,2784\%          & 0,2099\%          & 0,0077\%          & 89,7102\%            & 0,0537\%                                                                                                              & +0,2314\%         & +89,8780\%                                                                                                            \\ \hline
        +100\%                                                                                                 & 0,3199\%          & 0,2412\%          & 0,0088\%          & 99,6835\%            & 0,0617\%                                                                                                              & +0,2660\%         & +99,8668\%                                                                                                            \\ \hline
        \end{tabular}
        \label{tab:sensib}
        %\legend{Fonte: Próprio Autor.}
    \end{table}
\end{document}