I'm writing, not becuse I've any great answers, but in your shoes I'd not want to feel alone.
My family history is not a good one so I'm probably not the best to speak. I do know children, even when they become adults, see parents as a comforting and fixed corner of the world. Somewhere they can rely on and give and feel love.
When that breaks down the effect is huge, no wonder you feel hurt. It may be that both parents (even your mother) may love you, maybe just not each other. I guess you will be a better judge of that.
Breakup means the permanent becomes impermanent, and that certainly is terrible for your anxiety - how can I answer that? Well, you have faced adversity throughout you life, and have talked about much here. That does have an up side, believe it or not, you have coped with everything, and that may help you be more confident with the future, no matter what life throws at you.
I know I felt my parents, when I was young, were pretty good and loving people, and it does come as a shock if you find out that one, or both, are not what you thought. It can leave one feeling rather lost.
May I ask what you are planning, maybe support your dad?