Well TKD is taught to the Korean Military as their hand to hand training so I assume it has some combat value. Our grandmaster has a book out called "Tae Kwon Do Actual Fighting" it is by Tae Eun Ha. I have not taken a look at the book but from the title and what I know about his history (he used to teach TKD to the Korean Military) there is a good chance that it might be what you are looking for.
Sure. It's called taking the time to find a teacher that matches your goals. Many TKD schools have a sports focus or a character improvement focus that runs contrary in my belief of really teaching the art as a combat art. That said, there's been enough discussion on this board from a multitude of serious martial arts to indicate that effective combat skills is indeed a goal of teaching for many of us.
It's like tai chi. There are lots of teachers in the US who only teach it on a "healthy" crunchy granola level. But if you are lucky enough to find someone who really understands the art and is willing to transmit their knowledge, you'd be learning one of the most effective fighting systems anywhere. Same with karate or judo or any other martial art.
I would say there is, but if you mean a institutionalized art form than I would say NO. EXCEPT what is currently taught in the Korean or other militarys in the world.
One of my student's father was in the Korean military and he was watching my classes and he told me briefly about his training and said it was all about SD and fighting hand to hand. From the sounds of it pretty basic and hard style stuff. Nothing real flashy, except for the demo teams.
Any military will use any thing that works from a martial art, if it helps them meet their objective, training the soldier to capture, hurt, maim, or kill the enemy and win, then it would be called combat insert name here in my book. But the military objective for the system of combat is different than the civilian version of a martial art.