Re: Hughes.  Yes, I think you're right that they were no longer lovers at that time.  But you didn't change "was her lover" to "had been her lover," you just deleted the entire paragraph, which I dispute.  Instead, I propose:  With the help of Howard Hughes, who at one time had been her lover, she purchased the rights to the play and turned it into a hit movie.  The movie was very important to her career and it's an interesting and pertinent detail that Hughes was so involved in helping her make it a reality.  I certainly don't want to perpetuate errors, but let's talk about how to fix them instead of just deleting information wholesale.

Re: Hepburn and Tracy's living situation  what would you suggest instead?  How about something like... Hepburn and Tracy were undeniably a couple, but only lived together regularly until the last few years of Tracy's life. Even then, they maintained separate homes to keep up appearances.

Re the Hughes/Hepburn engagement  I believe there was a NYT article that announced their engagement, or announced that it was off, but I haven't had time yet to find it.

Re Hepburn and Smith's marriage, from Higham:  The marriage was a disaster. Kate had such a horror of domesticity that the whole experience was a nightmare. She evidently realized that she had married on a whim and that marriage was totally incompatible with her need for absolute freedom of thought and action.  Three weeks after the marriage took place, the couple separated.  Faced with the fact that he had a failed marriage, Luddy sensibly decided to continue with Kate on a platonic basis.  She remained legally married to him for several years.  Do you have something that refutes this?  I'd be glad to source it specifically to Higham in the text of the article if you like.