I'm going to break off my engagement over his father's racist remarks
Has his father personally insulted you?
No. I'm breaking off because he's insulting my family in general
You shouldn't feel pressured to get married if it doesn't feel morally right, but don't let your partner father influence your relationship.  It's wrong to make racist remarks, but if you really love your partner you wouldn't just give up on him.  Give it some time before you make any rash decisions, your partner's dad should apologize if he values your relationship with his son.
Don't tell me what to do.
If your relationship is harmful to your mental and emotional well-being, it may be best to give it a little space. It may be a good idea to talk to your fiance about how you are feeling before you make any changes.