I have a clue that may help with regards to Meir being the son of Moses:
From Dubno Yizkor Book, 'Dubno Rabbis' (https://www.jewishgen.org/yizkor/dubno/dub061.html#Page87):
"It is generally considered that in the years 1642-1643, the rabbinic seat in Dubno was occupied by the Gaon, Our Teacher Meyer Katz, son of Gaon Moshe Katz Ashkenazi. This opinion is supported by the script on the tombstone in the Dubno cemetery.
A righteous and holy man, a revealer of wisdom and Halacha,
Our Rabbi and Teacher Meir the son of MAHARAM Katz,
He passed away on Tuesday, 3 Kislev.
May his soul be bound up in the bond of everlasting life.
Maharam (Our Teacher and our Rabbi, Rabbi Meir) Katz was at first the Rabbi in Amstibovo and afterwards in Mohylev (Mohyliv, Mogilëv, Mohilev, Moghilau, Zogilów, Mogilev, Mohylów, Mogilov), on the Dnieper- (Molev) until 1642. Later he moved to Dubno and died there. Relying on the clause “…an illuminator of wisdom and Halacha,” one may assume he was the head of a college and a righteous teacher in Dubno until the day of his death. "
As you know, Otser Rabanim asserts that Meir # 12862 is the son of Moshe # 14463 (Dayan of Frankfurt), asserting also a son of Moshe's named Eliezer (# 2521; may have died in or around Zlotchov). There is no mention in Otser of Shmuel Zanvill. Jacobi also confirms Meir b. Moshe (I believe Jacobi data is in the published papers, Vol. 2, p.3, 14.1, but that could be wrong).
Ele Toldot to my knowledge covers mostly persons whose gravestones were seen in Frankfurt, so this may explain why some of the offspring who died elsewhere do not appear in Ele Toldot.
There appears to be little doubt that Meir's father was Moses, and if Otser is correct, then this Moses was a Dayan in Frankfurt, and if the Dubno book is correct, then he was also known as a Gaon and Maharam Katz. I don't see any indication on the Ele Toldot record indicating that Moses Katz, zur Reuse was a Dayan in Frankfurt (or that he was a Gaon or known as Maharam Katz), but those facts could come from some other documents Ele Toldot, or elsewhere.
