You can build the stack as high as you want , but its only as strong as its weakest link.
If your suckin air at the bottom it wont make much difference on top.
Your tree line effecting your draft somewhat.....looks good though with the high stack next to it
Stove pipe tends to be the culprit because it doesn't really seal well in an air tight way.... Chimney pipe tends to be different because it has the insulation and creates a better seal generally by twist lock or other.
Stove cement is good but it tends to crack from expansion ......but its better than nothing..
There is a pipe sealant that is available that is flexible and wont crack and doesn't smell at far as I can tell. But if it did it would be temporary and also the much lesser of the two evils . (smoke in the house)
I have found that by sealing the stove pipe that as a consequence , it removed the smoke smell that can happen sometimes on a low burn with a BK. It improved the draft and burn times and combustion of the wood quality.