My advice is to stay put at this point and only make a change i9f there is a problem.
The lender sends the appraisal out to an independent to get the job done.
Ask the lender to extend the $3,500 credit because you have nothing to do with the timing of the appraisal or the completion of the appraisal. Once the appraiser comes out, it could take as long as a week or 10 days to get it back to the lender. Ask them to explain how you should be penalized for something that is part of their process?
Bottom line, if you like the loan, fight for what they said you would get.
Find out what the lock in procedure is with Plan B before you execute. Know you could wind up in the same position with them also.
Best to you,
Mark & Kari Shea
Shea Real Estate
Serving Greater San Diego