Again, what I have dug up was he wouldn't see her when he was in prison and didn't see her when he got out. She waited, then, I guess found out he was with another woman. That's when she finally divorced him. She would have taken him back. The show suggests that with their final meeting. He was just finished. Whatever the hook was, he removed it and moved on. I was mocked when I brought up astrology (it's my thing - sorry, not sorry) so I won't go into detail, I will just say their charts are very interesting and show both Fanny's obsessive nature, in general, but also their connection. Feel free to PM me if you want to know more.
In Funny Lady, there was a scene where she sees him again and he was wealthy - playing polo - she was still in love. I don't know if that really happened, but she never got over him. There is one story that he tried to get back with her in the 50s, but she turned him down.
One thing I give him credit for is, he never spoke or wrote about her and likely never took another dime. Maybe he was more honorable than people gave him credit for in later years, even though William used the name Brice, ironically he looked just like his father. Sad.
In any event, not knowing much about the man - a story had to be created as to his personality. The best they could come up with was he was a handsome, sophisticated gambler who, one would assume, was good in bed. Ramin had the right idea I think with his levitation trick - Nicky could make Fanny laugh.