Keep in mind that the "major rage fit" likely is coming from an intense mental pressure shift within him and not necessarily because he is wantoningly being aggressive and disrespectful towards you.

This does not, however, excuse his behavior.

Many with Bipolar would love that all behavior shown and expressed be wiped clean by those around by saying that it's the illness and not me so, don't blame me.  Well, it's true to a great degree.. it really isn't them.

Still... it is how they have learned to manage their symptoms and the expression of the symptoms outwardly. 

Your son is young and he needs to learn behavioral skills and de-stressing skills so that when he gets in situations that are pressing him downward, while the disorder is pressing him inward, that he not lash out or do anything that will be counter-productive and cause more pressure on him or those surrounding him.  It's a tool and/or skill in which to be learned by BOTH he and HIS Parents.

I'd mention the anger outburst to the pdoc but I'd also emphasis mentioning it to his therapist, if you have him one.  The therapist can help teach some tools and tips to YOU and HE in order to handle these outbursts - which he'll have again and again - without making everything worse for the 2 of you.

Yes.. You need to learn how to deal with someone with a chronic and often disabling disorder without losing your cool... you do this by going through therapy as well & joining any support groups you may find.

This is not to say you are a bad parent so you need to learn to be a good one... it will however, help you become a smarter more savy one in dealing with a child who has a mental illness and all that does indeed... roll with it.