Inside Vent pipe setup?

[Lawson111]

Hello all, been a couple years since I've posted because I have been having really good luck with my current shelter wood furnace until now. The past couple days I've been getting a lot of puff backs. I've read everything I could on how to fix/prevent that from happening and I think I have got it figured out. Pretty sure my problem is when I load the stove I like to leave the door open (while monitoring) and get it going good before I shut the door and after I shut the door I think I was setting the air intake knob on the bottom ash pan door to low. So I've opened that up a little more we will see tonight when I get home if the house smells like smoke.

But I was looking for some opinions on changing my current vent pipe setup inside my basement before it goes thru the wall and exits into my chimney. Hoping to maybe improve draft I'm thinking this might also be an issue with the puff backs, and creosote build up. I did my best drawing my current setup and what I want to do if you guys think it might help. I'm not an artist so don't judge haha.

Let me know what you guys think. Also a couple times I've opened the furnace door to check how it was burning and it flashed pretty good on me. This just started happening as well. Is this also from not enough air intake or could it possible be from low draft or maybe over draft?

Top drawing is current setup, bottom is what I was thinking about doing.