Hi, Loving Husband.
A good deal of what you say resonates with me. I have been married nearly 36 years and a few years ago realised that my wife has a personality disorder. I believe it is "avoidance disorder". There are differences, especially in that your wife seems to be more open to discussing and acknowledging the existence of her problems.
I wonder if it would help to lighten up a bit. In saying this, I know that my advice might be completely superfluous. You might be doing this already. But I realised some years ago that many of my denials were exacerbating problems rather than easing them. It sort of seemed as if the truth were too terrible to speak, so what I was denying must be true. This implies that I'm a liar, but there's nothing unusual about that allegation. As a corollary, if you can say something then it is possibly not true.
So when your wife claims that she's ugly, and goes on with other silly stuff, you do the right thing when you laugh. But how about: "If you say so, Darling, you must be ugly. You would know. I'm just a fool who doesn't know what a gorgeous woman looks like." Then possibly, you could pick some famously gross woman and say, "Now I realise what you're saying. That so-and-so is a bit of alright! Much better-built (or slimmer or fairer or whatever) than you."
Anyway, it's just a thought. I hope it may be helpful and not out of place.