No. Your spouse is your wife.

No, she was never married.

You can help your spouse whose mother is ill and refusing help and therapy because helps the spouse what to expect and helps to know what to do at the moment.

Your mother-in-law's brother is your spouse's uncle, but is not related to you.

A spouse does not have any right to a mother in laws inheritance unless they are named specifically in the ill. You could contest the will with an attorney but you probably wouldn't win.