Theme: Circles and a clear hint in 1- & 71-across. I’d suggest working on a corner, perhaps the upper right until you can see what the circles spell. That’ll give you a good start on the theme and that will help in doing the other sets of circles. For a “big hint,” skip to the bottom of this post.
1-across: Spelling kountz.
Specific clue hints:
River in 1957 Movie: If you’re young, you may never have heard of it. Sounds oriental.
SALT Topic: SALT is an acronym and so is the answer
Singer/actress Luft:… or _____ Doone
_____ avis: Avis is a bird, and this one is all about being uncommon
Midwest hub: Think airport
Model’s path: as in Project ________
Lawrence of Arabia figure: One of a great many in the movie; not a specific actor or part
Amo, amas, I love _____: Pssst, it’s a rhyme.
Hot desert wind: 2 words
10 sawbucks: a sawbuck is $10. Since the clue is slang, so’s the answer
Digital book file extension: you can guess the answer because it makes sense that this would be the extension
Hit for Guy Lombardo…Jimmy Dorsey: 2 words; has something in common with the answer to 16-Across
Gershwin opera heroine: Title character along with her love
Like much folklore: Well, it ain’t found in books
Things that lead to mergers?: (In case you didn’t know: Question marks indicate puns / plays-on-words) Don’t think business or marriage.
Billy Blanks fitness systems: 2 words, but neither is a word in English
Big theme hint: Each set of circles forms a word starting at the 12:00 spot if it were a watch face & proceeding clockwise.