Okay. Well, first off, I also have a very love/hate relationship with my dad. It was just me and my dad starting in 1992 when my mom passed away. Before that our relationship was rocky. He wanted a boy, and my mom was unable to produce that (due to cancer and age,) and so he was stuck with me. He just never "understood" me I guess... I don't know how else to put it. He was 43 when I was born, so he's 75 now.
Anyway, I think my dad also has some type of mental illness. I can't say bipolar for sure or not. He also has diabetes, which causes moon swings very similar to bipolar. But, I do think he gets paranoid and depressed. He's now on anti-depressants, after his last major heart attack. However, growing up he was depressed and he was of the mind set (due to his generation) that you don't talk about those things and you just deal with it. That's how he dealt with me, too. Just suck it up and take it. So my first question to you is your dad's age. He could be of that same age group, and therefore harder to talk to, (especially since you say he is undiagnosed, that's a good sign he never sought help.)
Next, you know this is an irrational fact that you blame your dad for what happened. Of course he had no idea that was happening to you. Have you made any steps with your T in healing yourself? Does he still live in the same house/town as before? Would going there bring up any post traumatic type symptoms. Have you told anyone else? Like your mom? It might be good to have another person in your corner who knows the whole story if you tell him.
My final question is... your dad's health. Is your dad in good health or poor health? or maybe you don't know. I tend to keep my dad at a distance although we live in the same town. He's in poor health so on the one end I am concerned and I don't want him to die. On the other end... I always say the wrong parent died.... which sounds horrible, but he has done some terrible things to me and my family. Then at the same time he has done good things. But, I don't want him to go with us being estranged. His brother just recently died (who also had a lot of mental health issues and was abusive,) and they were never able to repaire their relationship before he died. Now it is too late.
Lastly... my mother-in-law was sexually abused by her dad. She lived for many years in angry toward him and her mom (who just let it happen, and lived in denial.) When my middle son was born (her first grandson,) she decided to take him to see her dad. She also re-contacted her mom after 13 years of silence. Her dad apologized to her for all the wrong he had done, and they were able to find peace. Her and her mom continued to have issues, but resolved some issues although not all. Both are passed on now, but at least she has that. In one case it went very well, and the other not so well, but she is more at peace with both.
So, I do think you need to work through the damage of your rape. I don't know if you tell your dad or not. Maybe first make contact and see how he responds, then decide. If you do tell, have someone else there with you for support who knows the story.
Anyway, a novel for a novel.

I'm very sorry you had to live through that.