I will help as I can based on the details provided. I am a Mortgage Lender but NOT an attorney.
1-There is no right of rescission on a purchase for either buyer or seller, this is a right for refinance transactions, certain HELOC's, second mortgage liens, and some other non applicable loans.
2-Caveat is I haven't seen the contract but, the contract was written to, agreed upon and "BOUND" based upon the agreed sales price. The reduction at the table almost certainly nullifies this. It is a material breach.
3-The realtor: They are licensed and have certain enforceable penalties for violating the terms. What I would recommend is find out who their principle broker at their office is. Inform them that you will be taking legal action based on your experience. The "Principle Broker" (your realtor's boss) is very much in a vulnerable position here. They will be highly motivated to make you whole.
4-Do not bluff, contact a real estate attorney and follow through, and do it without delay.