Sei incorreggibile nella tua distrazione e nel tuo rifiuto di documentarti e di ricordarti di quello che hai letto nella documentazione.
Tuttavia, dopo aver aggiunto un paio di macro e un apio di pacchetti al tuo esempio minimo NON compilabile eccoti la tua tabella rimessa in forma decente, nn al meglio, ma almeno decente
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\documentclass[a4paper,12pt]{article}
\usepackage{rotating}
\usepackage{longtable, pdflscape, multirow, booktabs}
\newcommand\un[1]{\ensuremath{\mathrm{#1}}}
\makeatletter
\def\esmd#1 {\ensuremath{\cdot10^{-#1}}}
\def\espd#1 {\ensuremath{\cdot10^{+#1}}}
\begin{document}
\begin{landscape}\footnotesize
\centering
\begin{longtable}{*{11}{c}}
\caption{Main properties for MIRO galaxies detected by Chandra.}
\label{tab:MIRO}
\\
\toprule
\textbf{ID} & \textbf{Model} & $F_{0.5-2}$ & $F_{2-10}$ & $L_{2-10}$ & $L^{in}_{2-10}$ & $C_\textup{Line}$ & $C_\textup{NoLine}$ & $N_H$ & $\Gamma$ & \textbf{EW} \\
& & (\un{erg\,cm^{-2}\,s^{-1}}) & (\un{erg\,cm^{-2}\,s^{-1}}) & (\un{erg\,s^{-1}}) & (\un{erg\,s^{-1}}) & & & (\un{cm^{-2}}) & & (\un{keV})\\ \midrule
\endfirsthead
\multirow{4}*{D461} & $\Gamma_\textup{free}$ & 2.09\esmd16 & 5.95\esmd16 & 5.98\espd42 & 6.53\espd42 & 513.14 & 514.38 & 1.15$_{-1.16}^{+1.51}$ & 1.63$_{-0.47}^{+0.64}$ & 0.16 (0.00 — 0.43) \\
& $\Gamma_\textup{fix}$ & 2.07\esmd16 & 5.20\esmd16 & 5.85\espd42 & 6.69\espd42 & 513.16 & 514.68 & 1.73$_{-1.23}^{+1.65}$ & 1.80 & 0.17 (0.00 — 0.45) \\
& $N_{H} = 0$ & 2.22\esmd16 & 6.73\esmd15 & 1.48\espd43 & 1.49\espd43 & 514.18 & 515.59 & 0. & 1.39$_{-0.31}^{+0.28}$ & 0.17 (0.00 — 0.45) \\
& Reflection & 9.04\esmd17 & 1.92\esmd15 & 5.82\espd42 & — & 579.12 & — & — & 1.80 & 0.04 (0.00 — 0.22) \\
\midrule
\multirow{4}*{D540} & $\Gamma_\textup{free}$ & 5.27\esmd16 & 8.63\esmd15 & 6.79\espd43 & 1.36\espd44 & 555.82 & 555.82 & 21.54$_{-7.22}^{+9.52}$ & 0.87$_{-0.23}^{+0.25}$ & 0.00 (0.00 — 0.01) \\
& $\Gamma_\textup{fix}$ & 5.51\esmd16 & 6.14\esmd15 & 7.21\espd43 & 3.78\espd44 & 587.24 & 587.22 & 54.31$_{-5.18}^{+6.98}$ & 1.80 & 0.00 (0.00 — 0.01) \\
& $N_{H} = 0$ & 5.71\esmd16 & 1.12\esmd15 & 5.51\espd43 & 5.55\espd43 & 603.13 & 603.12 & 0. & 0.18$_{-0.11}^{+0.09}$ & 0.00 (0.00 — 0.04) \\
\bottomrule
\end{longtable}
\end{landscape}
\end{document}
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