I am not that big a believer in childhood trauma suddenly manifesting. It happens, but it is a lot more rare than claimed to be. Usually, when people escape the here and now to provide similarities from the past that they disliked, I find that it is more about avoiding saying those things about the trigger in the present.
Things I notice from your posts.
- Your wife suggested poly
- You were not a "joyful yes" to put it a la Galagirl
- You were ok while there was casual poly interaction
- You got uncomfortable when she got serious about someone
- On her end, she seems to have dived into poly without a look to see how you were coping
- You were losing time with her
- You were losing your home space with her
- Even his roommate's space was considered, but not yours (her roommate) - not even by your partner
The things you describe your father making you feel, I see you going through them at the hands of the boyfriend. On one hand, you are all gung ho poly. Hanging out together and all. On the other, you are being stripped of things you took for granted about a relationship - your exclusivity with your wife, your time with her, your home space.... and you don't appear to have had much of a say about it. And so on. These are unpleasant in their own right. You don't need a father explanation, particularly since you weren't aware of any lasting trauma from your father till the boyfriend came on the scene. He is just becoming an "example" - a placeholder for things you want to say about the boyfriend on a level of feelings.
It is hard to admit own vulnerability in the here and now.
In other words, you don't need to fix unresolved issues with your father so much as unresolved issues about her boyfriend.
Part of it is just circumstantial. Their NRE, your first concrete experience of your wife having a serious partner... these will resolve with time. Don't know if you need therapy for that.
But if you're headed into therapy anyway - and why not, we all need someone to listen and focus on us. Also compassionate attention feels good for its own sake - I'd recommend learning to work with your personal boundaries. You were a child when you failed to hold them against your father, but you are an adult now and failed to hold them against the boyfriend till you got traumatized enough to explain it as something fundamentally wrong with you (unresolved trauma for most of your life grade problem).
Whatever happens of your father, your life will be immediately improved if you can simply say "she has a roommate too. You can't do all your hanging out in my space" or you could tell your wife "I need more of your time" or, for that matter "I don't feel ready for this poly thing and your serious relationship. GO SLOW."
I am only bringing this up, because addressing things you have immediate examples for and can see immediate changes in is usually easier than working on them through distant memories that will get remembered and interpreted depending on your feelings rather than actual data. It is harder. In the process, you just end up building a monument to abuse that had become irrelevant to your life till you used it as a crutch. And you end up adding it to your present unnecessarily.