Applescript (PDF to iTunes): How to extract and/or write metadata with special characters? Help please :-) INTRODUCTION

Hello there,

Like always, I want to put in front that I'm not a script expert. I'm not even a basic coder. I just try to learn, little by little about coding when I have these challenges. Please be through enough for a Dummy!

PRECEDENT

I need to transfer the metadata information of the author of a PDF book to the Author tag in my iTunes library. 
(Yes! I got rid of iBooks and got back Books in iTunes)

Recently here in this site, with the help of one of the members I got a script problem solved. Or sort of.

THE PROBLEM

I say sort of, because even when the script will do the task flawlessly if no special character is in the name, the script has a huge limitation: It won't read, write or both, text containing special characters.

EXAMPLE:

Mercé Lamás del Jagüey Nuñez   becomes in iTunes  Merce\U0301 Lama\U0301s del Jagu\U0308ey Nun\U0303ez-

I appreciate your help to find a solution.
I need to automate this task to properly curate the +4000 PDF books in my iTunes library.

Thank you!

SCRIPT IN DEVELOPMENT

tell application "iTunes"

set sel to the selection

if sel is {} then display dialog "Please select something" buttons {"Cancel"}

repeat with i from 1 to count of sel

    set the_track to item i of sel

    set the_posix_path to POSIX path of (location of the_track as alias)

    set authorfield to paragraph 2 of (do shell script "mdls -name kMDItemAuthors " &amp; quoted form of the_posix_path &amp; "|  awk -F\\\" '{print $2'}")

    set artist of the_track to (authorfield &amp; "-") as string
end repeat  
end tell


GRAPHIC
You can use perl to convert escaped unicode character from ASCII text :

tell application "iTunes"
    set sel to the selection
    if sel is {} then display dialog "Please select something" buttons {"Cancel"}
    set tc to count sel
    repeat with i from 1 to tc
        tell (get item i of sel)
            set loc to location
            set authorfield to my getAuthors(loc)
            if authorfield is not "" then set artist to authorfield &amp; "-"
        end tell
    end repeat
end tell

on getAuthors(f)
    do shell script "mdls -name kMDItemAuthors  " &amp; (quoted form of POSIX path of f) &amp; " | /usr/bin/perl -ne 'if (m/^ /) {s/^ +[\"]?|\"$//g;s/\\\\u([[:xdigit:]]{1,4})/chr(eval(\"0x$1\"))/egi;print}' "
end getAuthors


Or python :

do shell script "export PYTHONIOENCODING=UTF-8; /usr/bin/python -c 'import sys; print (sys.argv[1].replace(\"\\U\",\"\\u\").decode(\"unicode-escape\"))' \"$(mdls -name kMDItemAuthors  " &amp; (quoted form of POSIX path of f) &amp; " |  sed -nE 's/\"$//;s/^ +[\"]?//p')\""