I am so proud of you for standing your ground and holding your head high at the family reunion. You go, girl!
Actually, your parents' actions had the opposite effect of what they intended. Their cold and unloving attitude gave a "bad witness" and brought "reproach on Jehovah's name." You dad's unappreciative and self-righteous shunning of you after you "saved his bacon" by bringing the forgotten meat was noted and commented on. Then when he lied about his reasons for treating you that way, he undermined whatever vestige of respect the others may have had for him and his beliefs before. The fact that he felt the need to deny that he was obeying a major teaching of his religion put it in a bad light as well. It exposed the hypocrisy of the "one true religion™."
Your sister is in a tough spot. Maybe one day you can be completely reconciled. It's shameful the way your parents are coercing her into going along with them.
Frankly, I'm surprised your parents even showed up once they knew you were coming. Some JW's in my family have tried to guilt me into not coming to family events by saying that if I did, they would not be able to. They did succeed in keeping me from the gathering that followed my dad's memorial service by threatening to create a scene. I guess they were afraid my "apostacooties" would contaminate the JW family and friends who would be there, even though it was at a public restaurant. When my aunt passed away, my sister treated the other family members to dinner after the service but was adamant that no one was to tell me about it, even though I had flown in from 1500 miles away, rented a car, and booked a hotel room just to be at the service. Not everyone agreed with excluding me, but no one spilled the beans. I found out later. As an aside, my aunt's will had been changed within the last year to name only one beneficiary. Guess who it was...
Anyway, I decided that from then on, I would go to whatever family events I was invited to without regard to who else was coming or not coming. If someone didn't want to show up because I might be there, so be it. Their loss.
About a year ago, there was big reunion for family on my mother's side. None of the JW's showed up, though to be fair, some had perfectly valid reasons why they couldn't make it. Regardless, my Extremely Significant Other and I attended and we were embraced with the love and kindness and hospitality you would expect at a family reunion, all from "worldly" relatives. Draw your own conclusion.
Congratulations for standing up for yourself, and for helping your family see the truth about how your parents are treating you and the real reason why. You're an inspiration to everyone here.
Thank you so much for sharing this story. Let us know how things go.