Is there any reason you cannot use wood stove sealant?
If you have never seen it before it comes in caulking tubes, you insert it into a caulking gun, and by cutting the tip big or small, it squeezes out the diameter you need to fill the hole. It hardens in a few minutes, but says to let it cure for 24 hours. I am not a patient man and yet had no ill issues with it.
This, along with stove gasket material (fiberglass rope) works well. It is cheap as well, maybe 6 bucks for 6 feet of it, comes in different lengths and diameters. I have used this stuff successfully to take a a cheap non-air tight stove such as the Vogelzang pot bellied stove and made it air tight. I used gasket sealant along with gasket rope, pop riveted it to the doors and added latches for a perfect stove. I think I spent $40 on materials and turned a $400 stove into one that was as good as a $2000 stove.
In your case though, I might suggest doing the latter. A smoker is not designed to draft, and I think you are seeing that. With carbon monoxide able to kill without warning, you might be setting yourself and your family up to be killed. A wood stove is one of the most efficient things a person can buy; their cost to savings ratio being HUGE...but that is a wood stove and not a smoker. I would buy a cheap stove if you cannot afford an expensive air tight stove and just make it air tight. But even left air tight, unlike a smoker the darn thing will draft and thus not kill you.
Subject: How To Seal DIY Wood Stove Leaks?
Built a smoker wood stove for outside use and new we're trying to use it inside. For a heater.
So it needs to be smoke tight. Which it isn't. It leaks along both sides of the top which just sits down on the sides.
And it leaks at the flue connection.
The flue was made to fit old drain pipe and doesn't exactly fit currently available 4" and 6" fittings.
I've got the flue elbow squashed in there right now but you can see daylight through the sides. I'm thinking maybe some kind of fireproof clay?
The top - removable for convenience stacking and clearing the interior - has angle iron sides on a 4mm steel plate. The angle iron can't fit snug on the plate because of the radius and that didn't matter outside but it does now. It creates a long channel that leaks pretty bad until it starts drawing well and then I guess still leaks though not visibly.
I'm wondering if there's a fireproof tape perhaps I could use there?
The top could be welded on of course and all leaks blocked but I'd like to keep the convenience of what I have if I could.
And before welding the top on I should rework the interior. The ashpan doesn't cover the whole floor so there's ash left when you pull it out and then you can't push it back in. Outside I'd simply rake it all out. Inside the house that gives rise to fine ash floating around everywhere... it's no good.
I need to build an ashpan that covers the whole area and then build flanges all around the sides so's no ash can get down the sides of that pan.
So I'd need to do all that before ever welding the top down if it comes to that.