Increasing Draft

I am trying to figure out if there is any way to increase draft on my system. (The wife nixed the idea of moving the stove for cost reasons). Would any of these help:

1) Adding an extra 2 feet on chimney (total chimney now 15 or 16ft, 8ft above roof, corner room installation)
2) Adding a draft inducing cap to the top - i.e Vacu-Stack (some have told me these can be prone to water leaks)
3) Changing the stove pipe from single wall to double wall (extra heat for better chimney warmth?)

this is straight chimney and I run it in cat mode 95% of the time. The chimney is on the northwest corner of the house, so I'm not sure about the wind - we get it in all directions.

This is an Encore 2n1 stove. This will be the 3rd season, I believe.

The issues are mainly smoke coming out when loading (not always, just sometimes, which is what made me think of the Vacu-Stack). The other issue is backpuffing, but this one is somewhat manageable if I sit in from of the stove for an hour before going to bed to watch it carefully and slowly turn it down. (My wife refuses to operate this stove because of this - she used be ok with running the Vigilant).

The chimney meets the 10-3 rule. It is Hart & Cooley double wall Class A. Only 12" or so is in the attic.

I have attached a picture of my monstrous external chimney. Also the pic of the trees is from west, but mostly in winter the leaves have fallen already.

One other thing I noticed yesterday when peeking in the stove is that the bypass is not fully open when the lever is fully opened. If I stop opening the bypass about 3/4 of the way the motion, the flap is the most open, but then it starts to close again slightly as you continue to "open" the lever. I wonder if this could be adjusted?

This is a 6" flue opening and 6" pipe.

I've got the double walled class A chimney, but the stove pipe is single walled. This gives out more heat in the room, but my stove is well sized and only on the very coldest days of the year do I struggle to keep the house warm. I could give up a little heat if it meant the draft would be better.