It sounds like your husband is emotionally abusive towards you. I know that is not an easy thing to face. But no matter how much pain your husband is in, there is no reason for him to take out his feelings on you verbally or be abusive in his language.
Taking responsibility for his pain is something he needs to do. He knows this situation was not caused by you and even if it possibly could be, you do not deserve to be treated in such a way. And since he is able to control how he acts in front of others, he is not suffering so much that he does not know the difference between acceptable and unacceptable behavior. Having PTSD is bad, but it does not mean he has the right to abuse you because of it.
Emotionally abusive people feel powerless, insecure and fearful. They do either do not want to accept how they feel or they cannot handle how they feel so they take it out on someone else, usually their partner or children. The abused person is made to feel powerless, worthless, question their own judgment and feel they are deserving of the abuse. They also may feel so controlled they are not sure how to get out of the relationship or even if they can.
You mentioned that you are considering the future of your marriage which says that you are seeing the situation you are in as harmful to you. This is good insight. Your marriage can continue to work, but your husband must stop using his son's death as an excuse to be emotionally abusive. If he can take responsibility for his actions, get help (therapy and/or self help) and make amends, your relationship can grow and become better. You also need time to heal from your experience. Being abused takes a toll and your self esteem can be low as a result.
The first step is to talk about this in therapy. You mentioned that you both have been in counseling over the years, which is a good thing. It means you are both open to asking for help when you feel you need it. You may want to consider going back to therapy, or bringing this topic up in therapy if you are still going.
You can also talk with your pastor if you attend church. Pastors are usually trained to help married couples with a variety of problems.
Self help is a great way for both of you to work on your own issues around the abuse and come together to help each other. Here are some resources to get you started:
The Secret of Overcoming Verbal Abuse: Getting Off the Emotional Roller Coaster and Regaining Control of Your Life by Albert Ellis and Marcia Grad Powers
The Emotionally Abusive Relationship: How to Stop Being Abused and How to Stop Abusing by Beverly Engel
The Verbally Abusive Man, Can He Change?: A Woman's Guide to Deciding Whether to Stay or Go by XXXXX XXXXX
You can find these books on Amazon.com or your local library may have them for you.
You have great sympathy for what your husband has been through. I can tell by the way you speak about his loss. You seem to be a kind and gentle wife. But you do not deserve to be treated in a way that hurts you. With some work and your husband taking responsibility for his behavior, you can have the marriage you deserve.
I hope this helps. Let me know if you have more questions.