I would be glad to help you today with your legal question.
In this case, the way to sue would be under a theory of intentional infliction of emotional distress. In order to succeed on this claim, you must show for things: 1) your husband acted intentionallyo recklessly, 2) your husband's actions were extreme abd outrageous, 3) your husband's conduct caused your distress and 4) your distress I'd considered "severe."
Generally, IIED claims are very difficult to prove. For instance, in your case, simply saying that you have PTSD from your husband's conduct may not be enough to show that he caused it and that it waa severe. To counter this, you would most likely need to provide medical support and testimony from a psychological health professional. If you have had an ongoing and we'll documented pattern of psychological treatment since the incident, that may help your claim.
Also, while everyone is different, the conduct of your husband is judged on a reasonable person level. So although your husband threatened to kill you, that alone may not qualify as "extreme and outrageous." This element of the IIED is fact intensive. If your husband said something to the effect of " I'm going to hurt you one day," a judge or jury may not find that extreme or outrageous. On the other hand, if your husband said something like "I'm gong to kill you" while he was aggressively walking towards you with a weapon nearby, that would make it a stronger case. The fact that you have witnesses near by gives you somone else who can testify besides just you.
So, in essence, do you have a claim? Yes, you might. Assuming the above discussed issues are present. However, IIED claims are generally difficult to succeed on because while one person may think something is extreme and outrageous, other people may not think that. That is why it would be highly prudent to retain an attorney in your jurisdiction who is familiarw with the complex legal procedures to file such a claim and to argue on your behalf that all four elements discussed are present.