Hello,
Together, you have more or less nailed it.
Louis' full name was R[eb] Aryeh-Leib b[en] R[eb] Ya'acov-Kopil ha-Levi
The single letter resh before each given name is short for reb, and simply means Mr.
Leib was the Yiddish everyday name, or kinui, given to men with the Hebrew given name Aryeh (or Yehuda).
Kopil was a common Yiddish everyday name for Ya'acov.
In a formal document, the two names may have been linked with the Hebrew word hamechune, which means 'known as', i.e. Aryeh hamechune Leib ben Ya'acov hamechune Kopil.
After ha-Levi, the inscription reads נפתר ב כסלו = niftar 2 Kislev, i.e. died on 2 Kislev 704 = 29 Nov. 1943.
Justin