I am a converted who lives with his non-muslims parents (not ahlul kitab) and I struggle a little bit with purity, especially when it comes to food. Can I eat with my parents out of taqqiyah (for the sake of unity, not fear) even thought the food is najis (however it is halal meat) ? My parents aren't happy when I do not eat with them.

You can refer to Sheikh Fayadh in the law of purity of non Muslims, and accordingly you can eat with your parents, provided that you do not eat haram meat.