Honestly, at this point, I doubt the father would do anything harmful if he found out Kaoru is actually a boy. He just doesn't seem like the type. He might be upset initially because manga authors think "misunderstandings are so funny", but nothing beyond that.
At this point, I feel like Kaoru crossdresses either because he's just used to it, or because he actually likes it, but hasn't realized or doesn't wanna admit it yet.
Edit: On another note, I could understand dropping a manga early because you don't like the humor or because you're upset by a recurring gag, but going through tens of chapters only to then get upset at a harmless gag that's been there since the start... I dunno man.
There's probably an argument that crossdressing isn't harmless etc., but currently I'm not wise enough to see it.