NoAgenda,
There is no reason to conclude that Nick is gay.
Nick has been trying to leave the apartment but something keeps him there. Finally after the scene with the broken nose, he takes the chance to leave with the drunken Mr. McKee. Apparently, he puts the drunk fellow to bed out of kindness. Mr. McKee is a photographer and as he sits in bed he gives names to some of the photographs in his portfolio, which also seems to sum up the events of the evening for Nick (the narrator.)
Beauty and the Beast.....Daisy and Tom Buchanan?
Loneliness....
Old Grocery Horse......the dumb husband?
Brook'n Bridge....a pun referring to the Booklyn Bridge and the Broken Bridge of her nose.