I think you have done an admirable job trying to talk and explain to your son about what this behavior does to you. It hasn't worked. It is my opinion it is time to discipline him. It is wrong for him to treat anybody in that manner so he should be punished. He should spend time in the corner or doing chores or some other thing that will make him feel like saying mean things to you is not in his best interest. You may be bi-polar but that does not take away your right to be a mom and teach your child how to treat other people in a kind manner.
Take care,
I am rooting for you,
Zen<font color=blue>

Progress is nothing but the victory of laughter over dogma.--Benjamin De Casseres