Very cold chimney won't reverse the draft

Hello all,

I've had smoke in the house issues in the past, and this community really helped me out so I'm hoping I can be saved once again.

I have a basement Regency stove and 2 90 deg. elbows right above my stove leading the chimney outside. It's been bitterly cold (-20 C) recently and I've been really struggling getting the chimney primed. There is a very obvious down draft that you can feel in front of the stove that extinguishes a lighter easily. I've left a heatgun running on high for upwards of 30 min pointed directly at the flue, but this isn't enough. I've also tried blowtorch/heatgun combo for approx. The same time. I've tried cracking a nearby window , and opening the door of the stove for a few hours before lighting (with above mentioned priming methods), all to no avail. Every fire I light these days has the smoke just billow out towards me for a few min before it catches and the draft reverses.

It makes sense that there is 3 stories of extremely cold, dense air pushing down on my little stove, so reversing the draft can be hard. I'm just not sure what else to try. Do you think I could use a small space heater for a few hours beforehand? Are there smokeless firestarters I could light to get some heat? I considered lighting some old coals with the blowtorch and leaving the door closed (air intake wide open), but I still worry about CO generation there.

I'm hurting here guys, any help would be greatly appreciated!! Many thanks in advance.