An excellent way to negotiate with the lender is to shop lenders and always have two approvals. They often fall all over themselves to win your business when they become aware of the other lender ready to step in. Also, many lenders will provide the lock with a float down feature in case rates move in your favor. This is something to ask prior to applying with competing lenders.
Just an idea.
Let me know if you know of anyone else looking for a new home.
Would love to help them save money.