Smoking a whole duck - when to remove from heat?
You cannot find the correct final internal temperature for a whole duck, because it doesn't exist. If you stop the cooking when the white meat is tender, you'll have very tough red meat. If you cook until the collagen is melted, you'll get very tough white meat. 

With whole birds, it is more popular to go the collagen route. Especially a duck, with its darker meat overall and sufficient fat in the breast area to insulate the breast meat during smoking and then lubricate it, is a very good candidate for it. 

To melt the collagen, wait until the duck thigh has gone up to 70 Celsius (160 Fahrenheit) and from then on smoke for 2-4 hours. In this case, the lower part of the range (2 hours) is probably better, to have a chance of a little bit of juiciness to remain in the breast.