For the damper, mark where you want it to be on the pipe, say 1 inch up. Make sure it will clear the stove outlet when you have it open. Do this at your workbench where you can have some control. Get a long drill bit that is used by electricians to drill between floors, they are usually 12 to 24 inches long. Get one that is about the same diameter as the damper rod. (at home depot or lowes or some hardware store) Drill one side then place the damper plate inside the doublewall, align it so that there is equal spacing all around the damper plate and push the drill through to the other side and start the holes for the other side. Once that is done, pull the damper out and drill through. After that, just install the damper rod through the plate and you will be done.
You can control the pull on the stove with the damper, but not an air infiltration leak. But, start with the damper and see what that does. Do that dollar bill test on the ash pan door. Also, you can use stove seal in a caulking tube for a temporary seal, it will produce varying results, but perhaps enought to help there as well. And, while we are at it, how is the gasket around the bypass door, the big one you open to load the stove? If N/G replace that too, gaskets are cheap.
You can control the pull on the stove with the damper, but not an air infiltration leak. But, start with the damper and see what that does. Do that dollar bill test on the ash pan door. Also, you can use stove seal in a caulking tube for a temporary seal, it will produce varying results, but perhaps enought to help there as well. And, while we are at it, how is the gasket around the bypass door, the big one you open to load the stove? If N/G replace that too, gaskets are cheap.
