The sketch of the missing girl which Joe Mannix looks at is a beautifully rendered illustration complete with elaborate flourishes indicating that she's wearing a fashionable contemporary outfit. As a rule, police sketch artists just aren't quite that talented. It's obviously the work of a professional commercial artist.
Mannix and Dallas are tied up in the car alone in the closed garage with the engine running. To escape Mannix kicks the side rear window to break it so he can cut his tied up hands with the broken glass. The glass breaks like a typical house window breaks and has sharp edges, but side car windows are made of tempered glass which would break into a thousand tiny pieces and not able to cut anything.
When Mannix is holding the savings account book the last entry is a withdrawal not a deposit for $20,000 but it is added to the previous balance of $100 to total $20,100.
The police are listening to everything in the apartment when Egan confesses as well as his order to take Mannix and Dallas out and kill them. Mannix knew this, and he knew that Lieutenant.Tobias had the apartment surrounded ready to break in. The entire fight was unnecessary, foolish, and reckless on the part of Mannix since he could have gotten Dallas and himself shot deliberately or accidentally. That is not what a responsible mature detective like Mannix would have done.