Well John,
If your dog stops on command, that is a good thing. If he persists, command him again. Distract him by moving him from where he is to another place. Refocus him on some thing else, preferably you.
If he refocuses on you, his hackles should go down. He should be confident in you as leader. If you act as if there is no big deal going on, he'll get the message.
I don't know what your stop barking command is but I often will just do this little sequence "hey" pause "enough" pause "come" and when the dog comes I pet it or scratch it or offer some little gesture of approval with a 'good boy' or 'good girl' or 'good dog' or some thing that verbally signals my approval for the dog's coming to me.
My objective is to have the dog refocus on me when it hears my voice. I certainly don't mean with anxiety or fearfully but with a recognition that good stuff comes with my voice, and that it doesn't have to worry about whatever it was barking at.
I try to remove what ever is getting the dog's attention by redirecting the dog to me, briefly, and let it know there is nothing to worry about.
If your dog starts to bark again, just a quick 'hey' pause to let the dog focus on you, and then 'come.' When it comes, a bit of praise. If it tries to return to the behavior you don't want, redirect the dog. Take away the focus of his behavior and replace it with a focus you approve of.
Sooner or later, with consistency and patience, the dog will stop and come to you and do some thing else. It doesn't have to be a complicated redirection ritual. It should be matter of fact. Hey. Enough. Come. Good dog. No big deal.
I really believe anxiety in a dog is in some measure a function of leadership. If you are calm, matter of fact, and comfortable in your relationship with your dog, the dog will feel your confidence. That is not to say there aren't times when corrections are appropriate but corrections should be many fewer than positive reinforcements.
The old saw about calling the dog and your blood pressure rising with every ignored call, and finally the dog comes on the sixteenth time when you are frustrated, and you must be profuse in your praise of the dog because tomorrow it might come on the fifteenth, and so forth. Call the dog and correct it for not coming sooner and it will surely be reluctant to see you in a happy way.
It doesn't seem to me that your dog has any anxiety or certainly no serious anxiety that training and consistency won't overcome.
Did I mention I type fast and that that ability unfortunately contributes to long, uninteresting, and uninformative pontification? This post is confirmation.
Mike A.
"I wouldn't touch that dog, son. He don't take to pettin." Hondo, played by John Wayne