What are your future plans for arguing with your husband? Can you both commit to always doing in your bedroom with door closed in low modulation voices or going somewhere else your child will not be witness these events? If you can't do this nothing you say to your child will have any meaning. If you can commit to this then sit with your child and husband and tell your child what you did was very wrong and you will never do again. Tell him you want him to forgive you and never copy this unacceptable behavior with anyone in the future. You must keep this promise to rehabilitate your childs behavior. If he does not correct in a reasonable time professional help at school or a private institution may be required.
Start a swear jar. Swear jars are effective ways to control swearing in the house. Swear jars will keep your child from swearing inside the house. It is also a great way to save up some money.
Another activity you can do to prevent swearing in the house is starting to punish your child in various ways. Not physical punishment, mind you! If your child swears, take his favorite toy or deny him his favorite food. This will enforce a reward system and mentally rewire them to avoid using swears.
Stopping him from abusing peers is a trickier situation to deal with. Although the measures you’ve been taking at home will contribute to him not swearing but your child still still might do it. If you hear him abuse his peers, you should immediately scold him. I understand that humiliating him in front of his peers is not good but it is still extremely effective.