Hi if you both like the humiliation aspect and it gets him off and will help get him off quicker I'd suggest 2 things, understand his fantasies and play them back to him in bed when he's fucking you, but make them slightly more extreme. For eaxmple if he gets off on the thought of someone fucking you, extend that to someone you both know and talk to him about them fucking you. I also agree with one of the other posters, give him a time limit, which could be 5 mins to start with, then take 30 seconds off each time you fuck him until have him down to 30 seconds and if he doesn't come in time ******* him off you.
You could work on the humilation and have a series of humilaiting forfeits if he doesn't come in the time limit you set him: e.g get a vasectomy, get cuckold tattoo from a female tattoo artist, get him to poposition someone in a bar for you, make him wear a cuckold t-shirt in public etc.
I think he'll learn to cum quickly