I am so sorry to read this update, Ryan. The road ahead with your father and his side of the family is unpredictable. They may cling to their racist beliefs to their deathbeds. Ideally, they might eventually realize that their racist beliefs have stolen precious moments with a beloved son and amazing daughter-in-law. The point is that YOU can't change them. So you're doing the right thing to set healthy boundaries to protect your fiancee and your own mental health.
One of the big lessons I learned when I married was to put my husband first, before my parents' wishes. You're learning this early, but you're doing the right thing by putting your fiancee first and not exposing her to the ignorance and foolishness of racist relatives.
I know you are likely heartbroken and stressed that your father and his side aren't celebrating this momentous milestone with you. It's never easy finding love so it SHOULD be something we celebrate together. Surround yourself with family and friends who do cherish what the two of you have.
Sending all my best wishes to you both.