Looking at the picture of your sliding air intakes, they are open pretty wide. If that is how wide you have them open when burning, that's at least half your problem. Too much air under the fire. Plus as others have said, load that sucker up.
All a baro will do is limit your draft. It won't give you more draft. As was said earlier, you may or may not need one. The only way to tell is to use a manometer (draft guage) to see what kind of draft you have. A manual vent damper is not recommended with a coal stove. (Here come the comments from the manual damper folks)