Staying Steadfast in Faith While Living with Non-Practicing Family: How to Safeguard My Iman Without Breaking Ties?

Salam aleykum dear brothers and sisters, I'm a South Asian living in Europe, and after returning to Islam, I've been striving to pray my five daily prayers and deepen my understanding of the Deen. But honestly, my family situation is making it a real struggle. My eldest sister married years ago to a man who appeared Muslim but later revealed himself as an atheist. She stayed with him and slowly became strongly anti-Islam-she mocks those who want halal food, criticizes Muslim dress like the khimar or abaya, says Muslims don't belong in Europe, and is completely indifferent to what's happening in Gaza. She has a lot of sway in our close family, and my other sister followed her lead. She lived with an ex-Christian atheist before marriage and recently had a ceremony she calls 'Nikah' with him. When I gently explained that an Islamic marriage is only valid with a Muslim man, she bluntly told me religion holds no importance for her. The rest of my family are cultural Muslims and see nothing wrong with any of this. We're all very interconnected, so their views constantly weigh on me. To add to the difficulty, I'm the youngest, dealing with a chronic illness, and rely a lot on my family's support. My sisters actually help me a great deal with my health needs, and I truly want to preserve our family bond and uphold the ties of kinship. But I'm scared of slipping into sin, giving the impression that I accept their haram choices, or weakening my own faith. How can I navigate this relationship with my older sisters and protect my Iman without creating conflict or crossing religious boundaries? Any Islamic advice or personal experiences would be so appreciated. Jazakum Allahu khayran.