Regarding that drier air on the west between the core and the spiral band...

I went back and looked at the visual sat images before the nightly blackout, and that could be seen as early as 0215Z, and definitely by the 0315Z. Of course then it was on the E and NE sides of the storm. You can see it start to peel away in a sense.

And since that was being fed by the Gulf at the time I'm not sure what to attribute it to except being near land, and the storm being so large it needed to be totally surrounded by water in order to maintain a tight structure.

Anyway then during the blackout it rotated over the N side which was near or over land, and that is when it really deteriorated.

Going back to the 0045Z visual sat image the clouds above the core are symmetrical, like a donut. After that you could see the core of the storm start to break down into the spiraling bands on subsequent images.

So in spite of the large eye and solid small core around the eye, it doesn't appear to have an annular structure any more.