Yes, Joe was Norma’s kept man. As stated previously, her suicide attempt was not genuine, but a tool, a tactic she used to break down Joe’s last bit of self respect, self worth. She knew exactly what she was doing and she succeeded in her machinations.
I don’t think being kept bothered Joe as much as knowing others knew he was Norma’s kept boy did. That scene in the men’s shop were Norma was buying him everything and the salesman passed the comment to Joe “if the lady’s buying, take the vicuña” was his way of letting Joe know it was clear he was kept. This explains Joe’s angry outburst to the comment. They may not of shown Joe and Norma in bed together, but in many ways it was made clear that they were in fact lovers.
Regarding the casting, some of the women and men originally approached for the roles turned down the script because of the nature of the relationship between Norma and Joe.
As for Gloria Swanson, she was not a “real life Norma Desmond” at all! Their only common thread was that both careers had peaked in the 20’s - but while Gloria moved on, Norma never did. I vaguely remember seeing a clip of Gloria talking about Norma from one of the chat shows (Cavett or Merv I think) when asked about it she said something like “I’ve known plenty of real life Normas - Hollywood is full of them!”
For me it’s hard to imagine anyone else in these roles - from that time anyway. Sure, you can always wonder “what if Mary Pickford or Mae West was Norma?” or “what if Clift or Brando was Joe?” But for me it’s pointless as I view this film as classically cast.
Regarding a remake or update - I don’t think an update would work. I can’t picture a star from the 50’s living in obscurity yet wealthy in the 80’s and having the script/dialogue work. It tends to veer towards something like the “Whatever Happened to Baby Jane?” remake with the Redgrave sisters. If one was determined tho, I think a remake true to the time of the original could work better. Casting though would still be an issue.
For the poster up above who suggested a gay remake - that could be interesting! Someone like Ricky Martin as a Ramon Navarro type, but maybe the Joe character is a bit more mercenary thinking he can get his break via the Ramon character; Max would still be the Ramon type’s first love who had to be hidden so acted as his butler/valet and while Ramon moved on, Max never did and waited always thru the string of lovers in the hopes Ramon will come back to him. Max even warns the Joe character what will be expected of him, but Joe ignores thinking some charm and flirtatious behavior will work the trick - but like in the original, while it won’t be explicitly shown, we’ll know when Joe finally succumbs. Not sure how the final scene would work though - maybe he’s dressed for a Ben-Hur or The Shiek type scene? Hmmmm...
Ok - clearly I’m way too bored tonight after writing all this! lol