There's no way we can fix this timeline mess.
Connie was pregnangt when Carlo beat her. That must have been 1946, or as some may say 1947. If the communion was in 1955 (which doesn't make much sense to me because of the Cuban revolution shortly after that) then Connie's oldest kid must have been eight or nine. If the communion was in 1958 or 1959, the oldest kid must have been 12 or 13.

The tombstone - well it's a mystery, but I guess, it's the last revenge of Bonasera.