While the father's appearance has felt sudden, as many people have stated before, at least the extra chapter helped close this arc nicely. And it's a nice call back to the grandfather with being able to tell them apart. The father can't because he doesn't even know them, and so didn't even realise it wasn't Itsuki he was talking to.
The fact there was no kiss though, I can't tell if we are being trolled or not. It may mean that Itsuki isn't a possible final girl, it may also mean that it's held off till the end if she is. There's multiple sides to this, multiple viewpoints to consider, and it's going to undoubtedly spawn countless theories on what it means.