Technical Question about how to make a seamless top down version of Habu Kit 70

I tried the store sample of this jacket on at the Habu store:

However, it just did not fit right. I am over 6 feet tall and the sleeves of the medium were too short for me and the medium was WAY too big for me. Also, the pattern is very hard to understand and it would have cost me about $100 as you can’t buy it alone.

So, I would like to make my own based on Barbara Walker’s Kimono pattern in her book, “Knitting from the top down”

A few questions before I cast on:

  1. I understand how she explained that the top of the kimono sleeves would be seamless, but how can I also make the sleeves in such a way that they are completely seamless? I.e. when I have knitted down to the bottom of the front sleeves, how would I join the bottom sleeve sections so they that are seemless before continuing with the rest of the body.

  2. Also, I notice that this jacket has a curve at the underarms that is kind of similar to the curve on schematic for this drops jacket:
    Any advice about how I would make this curve from the top down?

If I were to use this drops jacket pattern as a template instead knitting from the top down, how would I change the neckline so that it is smaller and is similar to the Habu pattern? Also, how would I lengthen the torso of the drops jacket?

Thanks to anyone who responds,