I’ve always wondered, and this is all from poor memory: in one of those flics, Leitner is suspended above a tank of ravenous sharks, yet at the end he attends Bond’s wedding. How did he survive that cliffhanger?
That was Licence to Kill. You got it backwards. At the beginning of the flick, Bond attends Leiter’s wedding. Later in the flick, the bad guy feeds Leiter to the sharks. Bond was married at the end of On Her Majesty’s Secret Service. I don’t think Leiter even appeared in that one.
In the books, Leiter was mauled by a shark in Live and Let Die. He later re-appeared in Thunderball with a prosthetic leg and arm. The movies completely re-arranged the timeline.
In answer to your actual question, the bad guys hauled Leiter out of the shark tank before he died, and dumped him where the good guys could find him. It was intended to scare the good guys off.
Did he ever get his Waldorf Salad?
In the non-EON, Connery film Never Say Never Again, the first black actor to play Felix comments about how one of Q’s exploding pens blew up in his face. Was that supposed to be some sort of (totally unnecessary) explanation about why he was black in that film?
Indeed:
Leiter: ‘Killing me won’t stop anything, Sanchez!’
Sanchez: ‘There are worse things than dying hombre!’
L: ‘See you in Hell!’
S: ‘Today is the first day of the rest of your life.’
Sybil made him one. 
Honor Blackman as Cathy Gale in The Avengers, before she left to become Pussy Galore in Goldfinger. The current “trouble” in the Bahamas is obviously a reference to Dr No (which she was not in).
Similarly, in Fleming’s novel On Her Majesty’s Secret Service we have the line
This is clearly a reference to Dr. No, which had been released a few months before the book came out. IIRC, there’s something about her having a tan.
But Dr No was set in Jamaica?
You’re right. Thunderball, which they would have been filming in 1964, was set in the Bahamas.
In the episode “Castle De’ath,” which aired on 2 May 1966, Steed gets a greeting card from Cathy Gale and remarks to Emma Peel “Whatever is she doing at Fort Knox?”
didn’t Bernie Casey play Leiter?
In Never Say Never Again. I saw it once back in the '80s, just because Sean Connery was in it.
It was just (IMHO) a bad remake of Thunderball, so I’ve pretty much forgotten it. It was like watching that awful '80s reboot of Mission: Impossible that was filmed in Australia. (No offense meant to the Ozzie contingent in the audience. )
I just saw Bruce Boa playing a Canadian airline pilot in “Dead on Course,” an early B&W episode of The Avengers. (S2, E14)