First , why are you running it when its in the 60's outside ?
.................BK'S need a good draft.
Second, your chimney height is just at the minimum for a BK stove.,.....That's the height I am at with my Ashford but mine is a straight shot up.
Because you have 2 elbows you will have to compensate for that loss of draft and add more height.
The BK's require MORE DRAFT than any other non-cat and secondary tube stoves to operate properly. If you don't get adequate draft with these BK stoves you will run in to all kinds of trouble. Like for example : Massive creo buildup inside the firebox caused from improper combustion of the wood because of lack of draft . Also you will have a smoke filled firebox a lot of the time which Is also caused by lack of draft in pulling up the smoke to combust the wood. That smoke in the box will also cause a smoke smell coming from the door . Especially if you have the t-stat turned too low.
And also the problem you mentioned with smoke coming in the house when you open the door
The t-stat relies on a good draft to maintain proper ignition of the wood . ...... without proper draft the t-stat will just keep opening to let more air in from your partially ignited wood and cause a smokey and too cool firebox with lots of creo buildup and in the chimney too.
Its the proper draft that keeps that t-stat opening and closing correctly , that gives you the quick ignition of wood so the t-stat can open and close effectively and work to keep the burn going the longest and most efficiently.
The t-stat is only as good as your draft...........And that's everything in BK technology
If there is no way you can increase your chimney height then I would run the stove on a higher t-stat setting to try and compensate for lack of draft.
Congrats on the Ashford by the way..........Great stove !