building confident of 2 years old boy?

My son is a smart, friendly enough and cheeky boy. To strangers who are friendly, he can be really friendly too. However, in the crowded loaded with strangers, he can be a different one, just stick with me and cries when someone approaches, while another children just keep being happy. If another child grab his toys, he would just look at his toys gone.

I understand every child is different, but it just so sad to look at him being bullied and can not stand up for himself. If I were there, it's allrite, otherwise how can he survive?

He is only 2 yrs, I don't know how to teach him to grab back his stuff. How to built up his confident?

My husband is moving to another city for 1 year, I am considering to move out with him or not.

I am so worried my son will struggling adapt with new childcare. If he is lucky enough to adapt, then he has to move again next year and struggling again, is it fair for him? Or is it better not to move with my husband eventhough it means my son can't be close to his father most the time?