It does not matter if a boundary makes sense to you. It does not matter if it seems inconsequential to you. Boundaries are the prerogative of the person who sets them. You do not know that person’s story, and they are not obligated to justify their boundaries to you. That touch that seems insignificant to you may be uncomfortably intimate for someone else. That interaction that is fine with others may trigger someone’s PTSD. You do not know more about someone than they know about themselves. Trust that they know what they are doing when they set a boundary with you, even if you do not understand why.
When someone sets a boundary with you they are saying “no.” No means no. Do not push people on their boundaries or ask for explanations that are not readily given. Doing these things indicates that you do not respect their boundaries. For many people, saying “no” once, setting a boundary, is difficult enough. Do not put them in a position where they must repeatedly do so. No means no the first time. Pushing them on it suggests a hope that you can wear them down, which is problematic at best and predatory at worst. No means no.
The response to “this thing you do makes me feel unsafe or disrespected” is “I hear you, and I will not do that thing that makes you feel unsafe or disrespected anymore.” It isn’t “I love you.” Listening is the required act of love. “I love you” comes after that love is in evidence, and not before. Or instead.
If he stomps off in a huff or gets very negative and shitty, like “SEE IF I TRY TO HELP YOU EVER AGAIN, UNGRATEFUL DAUGHTER” it means you’ve won. “Really, Dad? You can’t even give me a break from constantly advising me for 6 months? Did you raise me to be able to handle my own life or not?” Hold your ground. He’s retreating in the hopes you’ll follow. Don’t follow. Just sit with his negative emotions (and let him sit with them) and don’t try to soothe or fix it. Let it be weird and uncomfortable. You didn’t make it that way. HE made it that way when he deliberately ignored your stated boundaries. Don’t be the first to apologize. Let him come to you.
Another great post from Captain Awkward.