What did he mean by "i look like our father"? Who's our ?

he means "ours" as in his and his mother. Its the same as a mom saying "daddy says this: " The father of the family so his mum falls under the umbrella of the dad being the "dad" of the family hierarchy.
That made no sense haha but its commonly said in Asian households. It just translates funny.

Now thats confusing #－.－)

He was taking to his younger self in his head

Okay that makes sense