I just held up an incence stick and the smoke was blowing back at me. When I open the door I can immediately feel wind blowing at meIt looks like they didn't cap the tee and it's an 8x8 flue tile. The uncapped tee is hurting the draft. It's possible, you may not need an ERV or outside air, just a different stove. If you close the damper on the stovepipe. Then open the cleanout door and hold a burning incense stick or cigarette by the cleanout door opening, does the smoke get pulled up into the chimney? If so the draft is present, just leaky.
We're not going to answer all questions tonight. I'll pick this up in the morning. @bholler may have some thoughts on this too.
what does capping the tee mean, would soot still fall down to the door and how would I go about doing that?
Have a good and look forward to chatting more. We really appreciate it.