It's fairly simple language that a 12 yo can understand. Texts are not ideal tools to use in this situation. I am sure he would have preferred to call and explain but when a relationship goes to shit and the other side can't be trusted not to make false allegations (AE with Ella as her pawn) then written communication is safer. The fact is, it's not, right now, a kind and loving father daughter relationship so he is just acknowledging that. He still loves her of course but he is fearful too.The way he says it’s not a “kind and loving father daughter relationship” like he is addressing another adult.
It's easy to judge IG for not being "perfect" here but also very obtuse. He has to tread carefully with Ella, sadly.