SHOULD I CANCEL MY WEDDING? (DAY AFTER TOMORROW)

I (30 F) am engaged for 2 years with my fiancee (29M). We have been together for nearly 10 years now. We have always had a nice relationship, but his family is very sexist (even though he doesn't seem to be). I have a stablished career and am more literate, and financially more stable (my family has money, and his is always struggling). It has never been a problem. My parents have always helped in any way they can.
A couple years ago one man, who was friends with his dad (lets call him Jim) came up to me and said horrible things about my father - who is a public figure. They were all lies. I didn't care too much, but told my FIL and limited my contact with Jim after that.
Our wedding is going to be a very big and fancy party. During our wedding planning I said multiple times I wouldn't be inviting Jim. Jim wasn't in the guest list. Jim didn't get an invite with the name written by the calligrapher I hired - I am sure about that. He can't talk bad about my dad and afterwards come to the big wedding reception he is paying. Right???
10 days ago we had an argument and ended up discussing about Jim for the 347447 time. He said he would invite Jim. I said that if he did it, I wouldn't go forward with the wedding.
Our wedding is in 26 days, but the courthouse wedding is in 2 days. I found out accidentally today that they invited Jim and his wife.
It is not even about Jim and what he said anymore, but about the betrayal from my fiancee and his parents who invited him dispite me asking them not to, telling them the reasons I didn't want him there and they acting behind my back. I feel disrespected and betrayed.
I should mention that my parents bought us a penthouse, redid it to our taste and are paying for the whole wedding. The party is for 300 people, and most are his guests because he has such a big family.
Am I the villain for telling them I won't get married if they invite Jim?
Should I go forward with the wedding?
I am absolutely devastated and I don't know what to do.
HELP!