It sounds normal to me, they are very confused and angry about the change and tend to take it out on the person they trust the most. When Dh and I were moving we ended up in different countries for nearly a year, our Ds was mad as hell and very confused, he started hitting too. I used to wrap his arms around his front and hug him and whisper sweet things in his ear while I held him close in a bear hug, tell ing him how much he was loved kissing him on his ears/head wherever I reached and telling him he couldn't hit anyone that wasn't nice etc etc, I just kept on doing it each time he would lose it on me and he seemed to get better over time. He will settle eventually, but she shouldn't allow him to hit her without doing something about it.
It's quite common....I've never smacked my DD, she's never been smacked, even by other children particularly so when she started hitting me I was gobsmacked. It is usually out if frustration and anger. They're still babies and it's their way of expressing anger. The advice about bear hugs is great advice. I just used to say in very soft, very calm voice "please don't hurt mummy. No. It makes me sad. No". Then distract her. If it was part of a tantrum, I'd walk away then as soon as she had calmed down enough I'd go back and cuddle and distract with a game etc. Good luck x
After move he seems to be happy settle down so not reason for dc behaviour
The world he knew has been turned upside down - his behaviour is the only way he can express that. It takes time, but as long as both him Mum and Dad keep reinforcing how much both of them love him, he'll adapt.