A. How frustrating not to be able to get a break from the bedtime ritual! It's great that you want your son to learn to accept Daddy. This isn't always easy, however, particularly if it's you who are with the baby all day long. Your son has clearly learned that you are special to him, which tends to happen at around 4 to 5 months. He's only going to get more intense about your relationship as he heads into the second half of his first year, with the arrival of stranger anxiety and separation anxiety. It is better, then, to get your son comfortable with his father as soon as possible.
Does your husband ever give your son a bottle during the day? That would be a good place to start, since daytime bottles are generally less associated with ritual and your son will probably be less tired than at night. In general, any extra time Daddy spends with Baby during the day will increase their comfort with each other. Ideally, you should stay out of the way during these times; it's not uncommon for mothers to interfere with their husbands' efforts at taking care of the children, unintentionally undermining his efforts. It's fine if your husband interacts with the baby differently than you do -- children will rapidly learn and accept that moms and dads have different styles, and can actually benefit from this.
Letting Daddy play a smaller role in the bedtime ritual may help your son associate his father with this time of day. Dad could start by taking over one aspect of the preparations, like changing the diaper or giving Baby his bath, and then stay around for the rest (like sitting with you as you feed him), gradually taking on more tasks.
Failing all else, you may just have to let father and son tough it out one night without your intervention. There may be some tears, but it's important for both of them to learn that Daddy can soothe the baby.