I am so very sorry that you and your family are living through ODD with your son, I have no idea how that must be to manage everyday, I can hear how frustrated and hurt you are but so very very brave and so loving in what I can only imagine to be a heartbreaking environment.
I know you know this but your son really does not come from a place of malice or hate, that he does have a mental illness and is not choosing this. It is so great to hear that you have a wonderful husband who is supportive and that you sound like you have a great relationship in such a hard time. Your son is so very lucky to have such support in his life.
I am by no means a professional but I am wondering if instead of pointing out the pain that he is causing when he says these things if infact you could change your response to him. You mentioned " I don’t understand how my son doesn’t see this. I stare in disbelief at what comes out of his mouth and tell him that his words are hurtful and is impacting his dads mental health. He just does not care and swears at me saying that I always side with hubby"..he doesn't see it(the pain) as his mental illness prevents him from doing so, so I am suggesting that saying these things to him about how much he is hurting his father and you too does not impact him....I am thinking that maybe in times that he says such things as "you should commit suicide" that you dont actually respond with words but with a hug. The act will go against everything his brain is expecting and also change the way you feel too. I am by no means a professional here but the power of human touch is undeniable and I believe that people who suffer ODD are not malice people filled with hate, that perhaps the power of being held can reassure him his is loved, that his illness is not who he is as a person, and it may also give both you and your husband time to hold your son, knowing he really does not mean these words.
I am so glad you do have some professional support and your son does too, are there perhaps some support groups that you can join with other parents who are dealing with this illness also, that might be really helpful to share and to hear how they are coping.
I hope to chat to you some more, huge hugs to you.