I am sorry your husbands family are ignorant and do not want to know about your condition.
As for the handicap placard people just keep their mouths shut and move on.
Some people have it for alot of things you may not be able to see such as a bad heart, breathing issues, headaches, fibro and other conditions. Some people just have nothing better to do than give others a bad time.
I hope you have a wonderful holiday and Happy New Year.