Is there a minimum or maximum USD Balance or Yield that can be accepted?

There is no minimum USD balance to earn Yield, but there are 2 things to note:

You will receive a yield of at least $0.01. If the yield you should receive is $0.00987 then you will not receive any yield.

There is a maximum average balance that can earn yield of $100,000. If you have an average balance of $150,000, you can only earn yield on the $100,000 you have.