BTW - I think I will be learning from the wisdom from this board too. My Dad had bpd (I was his emotional caretaker from a young age). My ex husband has bpd. I see him only several times a year. My entire life has been influenced by this illness.
This is important information. Our childhood experiences and family dynamics have an influence on us. Understanding this isn't about blaming them- that isn't useful, but it is helpful to us to understand ourselves and our own patterns of behavior.
When a child grows up in a family with a disordered parent- the family dynamics are what the child experiences as "normal". It's the only experience they know. The child learns behaviors that may help them function in their family of origin but are not functional in their adult lives. Learned behaviors can be changed.
One can still have emotional responses from childhood. Likely your father was scary- at least emotionally- and you learned that appeasing him and enabling him helped you to feel safe. This is a familiar response for you. When you don't do these behaviors that helped you to feel safe- you now feel the emotions that these behaviors were managing.
Now for the realization that these are self serving behaviors. While enabling your son may seem like helping him, they are actually managing your fears. Now is your opportunity to learn other ways to self regulate, ways you weren't able to learn when growing up in your FOO. You had a real reason to have them as a child. You were helpless, your Dad was in charge and he was scary. Now, as an adult, the situation is not the same and you can change these behaviors, but it can take some practice and learning, and everyone starts where they are, on their own path.