It's disgraceful that your employer is using your surgery as a means to get rid of you, I'm sure that must be against employment laws. I'd give ACAS a ring over that one, you might have a case.
Also, sorry to hear about your mother-in-law, the death of a close family member is shocking and devastating. At least you and your husband can be there for each other, and I hope in time you can come to terms with your loss.
I wish you all the very best with your surgery x