That's it. I've seen the whole episode and read your really long text.
Maybe I didn't get everything right on from the start because I feel heavily tired...
I liked both ending actually, in their own ways. The original one because of it's touchy ending, reunion when Yomi thought all was lost. Yours because of the turn of Yoki, he turned good again.
I didn't have any idea who that old lady was and how in hells name she could've know that they were there or anything about the shadow something. So, your version sounds more logical and correct in my ears. You write really good, and you got one hell of an imagination. It felt as if you got all the personalities and everything believable and correct.