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.