2) Yes, that's what "deuce" means in tennis.
1) Not really. It is a strange sort of encouragement.
If Charlie wants to play in the Wimbledon championships someday, he needs to win a lot of games. Charlie's brother is using a common pattern of words. It is indirect. Let me try to explain it.
The overall plain meaning is "You are losing."
He is pretending that Charlie has said "I want to go to Wimbledon." Charlie has a dream.
He is saying Charlie is losing. He pretends that the reason is that Charlie has forgotten his dream.
It IS a KIND of encouragement--goading, teasing, needling. It is a two-part message:
a) You are losing. -- Negative
b) Remember your dream! -- Positive