I've had similar issues with my bf. I'm pretty sure now that he would be the perfect cuck. I mean he's got all the right assets. He's submissive in bed (wants to wear my panties, wants me to sit on his face etc.), his dick is just about average in length but super lacking in girth, masturbates to interracial porn and even some cuckolding porn (I've seen his history). But even despite the above and the fact that I can visibly see his dick gets hard, he gets angry whenever I drop a remark about the size or sharing me (It's got better though.) I recommend being more dominant with your husband, watch movies with interracial/cuckolding sex - in particular those ones where the size difference is clearly visible and hint at it frequently. I think that one day he'll finally accept the reality and give it a go.