I think he was just frustrated about everything changing too fast and him not being able to keep track of what was going on or do anything about it, it was just another thing on a list, and–wait. Do you mean venting in this episode or before, after he first found out? I think at that point he was mostly just shocked and feeling like it was another sign he didn’t know his kid and then there was also the fact that he’s Val’s father in Juls’s father’s body, lol.
Overall, I think he’s a temperamental dude, his moods seem to influence his thoughts. In last night’s ep, after being in a better place to have a longer chat with his daughter than the last time, he noticed how unhappy she was and well, he’s spied on them enough to know how good Juls is for her. How else should any loving parent advise his daughter?