I understand it’s been a while since your post, but I wanted to reach out.
Your feelings are completely valid. Grieving your father is completely valid. I’m sorry that you weren’t able to celebrate him with the rest of your family; everyone grieves differently. Have you been able to find a way to bring him into your life and celebrate him a little? You sound like an amazing person. Being affected by grief in this way wasn’t your choice and it sounds like your taking some fantastic steps with your family.
I hope everything has been well and continues to improve,