Is a 7 good enough?
A 7 is the floor, not the goal. The norm is an average of 9.0. A 7 means the client is not leaving this month and is not referring you either. It gets a conversation, not yet a decision.
What if the 6 is my biggest client?
Then the conversation matters more, not less. Your biggest client under a 7 is your biggest risk, and usually the one that needs the most of your own hours. Fix it first. If it cannot be fixed, plan the exit before they plan it for you.
Should I tell the team the scores?
Yes. The meter belongs to the team. When the team sees a 6, they know what the standard is and what happens next without asking you. That is how a happiness problem stops becoming an Autonomy problem.