When Dorothy and Jack talk on the front entryway, he is directly facing the doorway. When Dorothy opens the front door, nobody is standing behind her or anywhere in the doorway.
Mammy calls Blanche "Blanche Marie" in another episode Blanche states her name is "Blanche Elizabeth".
When Blanche expresses disbelief that Big Daddy and her black nanny had an affair, she claims that Big Daddy was a Republican and thus wouldn't do that sort of thing. However, it was the Democratic Party that mostly legislated Jim Crow laws from 1865 to 1968. This was especially true in Georgia where Blanche grew up. The Republican Party largely opposed Jim Crow laws across the the United States. Therefore Big Daddy had probably been a Democrat as far as Blanche knows.
Mammy scolds Blanche by referring to her as "Blanche Marie" but later episodes reveal her middle name to be Elizabeth.